diff --git a/src/astprinter.rs b/src/astprinter.rs
index 6024e95..5da275f 100644
--- a/src/astprinter.rs
+++ b/src/astprinter.rs
@@ -1,4 +1,4 @@
-use crate::expr::{Binary, Expr, ExprVisitor, Grouping, Literal, Unary, Variable};
+use crate::expr::{Assign, Binary, Expr, ExprVisitor, Grouping, Literal, Unary, Variable};
 use crate::stmt::{ExpressionStatement, PrintStatement, StatementVisitor, VarStatement};
 
 pub struct ASTPrinter {
@@ -59,12 +59,21 @@ impl ExprVisitor<()> for ASTPrinter {
             Expr::LiteralExpr(l) => { self.visit_literal(l); }
             Expr::UnaryExpr(u) => { self.visit_unary(u); }
             Expr::VariableExpr(v) => { self.visit_variable(v); }
+            Expr::AssignExpr(a) => { self.visit_assign(a); }
         }
     }
 
     fn visit_variable(&mut self, v: &Variable) -> () {
         println!("{}VARIABLE(name={})", self.ast_tab(), v.name.literal);
     }
+
+    fn visit_assign(&mut self, a: &Assign) -> () {
+        println!("{}ASSIGN(var={}", self.ast_tab(), a.name);
+        self.depth+=1;
+        self.visit_expr(&a.value);
+        self.depth-=1;
+        print!(") ");
+    }
 }
 
 impl StatementVisitor<()> for ASTPrinter {
diff --git a/src/environment.rs b/src/environment.rs
index 7b761fa..6f8766d 100644
--- a/src/environment.rs
+++ b/src/environment.rs
@@ -23,4 +23,13 @@ impl Environment {
             None => { Err(RuntimeError { message: format!("Variable {} non définie", name) } ) }
         }
     }
+
+    pub fn assign(&mut self, name: String, value: Literal) -> Result<(), RuntimeError> {
+        if self.values.contains_key(&name) {
+            self.values.insert(name, value);
+            Ok(())
+        } else {
+            Err(RuntimeError { message: String::from("Undefined variable")})
+        }
+    }
 }
\ No newline at end of file
diff --git a/src/expr.rs b/src/expr.rs
index 6d6f8a0..1542b72 100644
--- a/src/expr.rs
+++ b/src/expr.rs
@@ -1,5 +1,11 @@
 use crate::token::Token;
 
+#[derive(Clone)]
+pub struct Assign {
+    pub name: Token,
+    pub value: Box<Expr>,
+}
+
 #[derive(Clone)]
 pub struct Binary {
     pub left: Box<Expr>,
@@ -38,6 +44,7 @@ pub enum Expr {
     LiteralExpr(Literal),
     UnaryExpr(Unary),
     VariableExpr(Variable),
+    AssignExpr(Assign),
 }
 
 pub trait ExprVisitor<T> {
@@ -47,5 +54,6 @@ pub trait ExprVisitor<T> {
     fn visit_unary(&mut self, u: &Unary) -> T;
     fn visit_expr(&mut self, e: &Expr) -> T;
     fn visit_variable(&mut self, v: &Variable) -> T;
+    fn visit_assign(&mut self, a: &Assign) -> T;
 }
 
diff --git a/src/interpreter.rs b/src/interpreter.rs
index 871ea6c..b406cb6 100644
--- a/src/interpreter.rs
+++ b/src/interpreter.rs
@@ -1,14 +1,9 @@
 use crate::environment::Environment;
-use crate::expr::Expr::UnaryExpr;
-use crate::expr::Expr::LiteralExpr;
-use crate::expr::Expr::GroupingExpr;
-use crate::expr::Expr::BinaryExpr;
-use crate::expr::Expr::VariableExpr;
 use crate::expr::Literal::LiteralString;
 use crate::expr::Literal::LiteralNumber;
 use crate::expr::Literal::LiteralBool;
 use crate::expr::Literal::LiteralNil;
-use crate::expr::{Binary, Expr, ExprVisitor, Grouping, Literal, Unary, Variable};
+use crate::expr::{Assign, Binary, Expr, ExprVisitor, Grouping, Literal, Unary, Variable};
 use crate::stmt::{ExpressionStatement, PrintStatement, StatementVisitor, VarStatement};
 use crate::token_type::TokenType;
 
@@ -153,14 +148,22 @@ impl ExprVisitor<Result<Literal, RuntimeError>> for Interpreter {
 
     fn visit_expr(&mut self, e: &Expr) -> Result<Literal, RuntimeError> {
         match e {
-            BinaryExpr(b) => { Ok(self.visit_binary(&b)?) }
-            GroupingExpr(g) => { Ok(self.visit_grouping(&g)?) }
-            LiteralExpr(l) => { Ok(self.visit_literal(&l)?) }
-            UnaryExpr(u) => { Ok(self.visit_unary(&u)?) }
-            VariableExpr(v) => { Ok(self.visit_variable(&v)? )}
+            Expr::BinaryExpr(b) => { Ok(self.visit_binary(&b)?) }
+            Expr::GroupingExpr(g) => { Ok(self.visit_grouping(&g)?) }
+            Expr::LiteralExpr(l) => { Ok(self.visit_literal(&l)?) }
+            Expr::UnaryExpr(u) => { Ok(self.visit_unary(&u)?) }
+            Expr::VariableExpr(v) => { Ok(self.visit_variable(&v)?) }
+            Expr::AssignExpr(a) => { Ok(self.visit_assign(&a)?) }
         }
     }
 
+    fn visit_assign(&mut self, a: &Assign) -> Result<Literal, RuntimeError> {
+        let value = self.visit_expr(&a.value)?;
+        self.environment.assign(a.name.literal.clone(), value.clone())?;
+
+        Ok(value)
+    }
+
     fn visit_variable(&mut self, v: &Variable) -> Result<Literal, RuntimeError> {
         self.environment.get(&v.name.literal)
     }
diff --git a/src/main.rs b/src/main.rs
index aff00d7..b6106a2 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -103,4 +103,4 @@ fn run(src: String) -> i32 {
 // https://github.com/munificent/craftinginterpreters/wiki/Lox-implementations#rust
 
 // Pause :
-// http://www.craftinginterpreters.com/statements-and-state.html#global-variables
+// http://www.craftinginterpreters.com/statements-and-state.html#assignment
diff --git a/src/parser.rs b/src/parser.rs
index 3f7af2e..059301c 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -1,4 +1,4 @@
-use crate::expr::{Binary, Expr, Grouping, Unary, Variable};
+use crate::expr::{Assign, Binary, Expr, Grouping, Unary, Variable};
 use crate::expr::Literal::{LiteralBool, LiteralNumber, LiteralString};
 use crate::token::Token;
 use crate::token_type::TokenType;
@@ -92,11 +92,28 @@ impl Parser {
         }
     }
 
-    fn expression(&mut self) -> Result<Expr,ParseError> {
-        self.equality()
+    fn expression(&mut self) -> Result<Expr, ParseError> {
+        self.assignment()
     }
 
-    fn equality(&mut self) -> Result<Expr,ParseError> {
+    fn assignment(&mut self) -> Result<Expr, ParseError> {
+        let expr = self.equality()?;
+
+        if self.match_token(&[TokenType::Equal]) {
+            let value = Box::new(self.assignment()?);       // l'assignation a une associativité par la droite
+
+            match expr {
+                Expr::VariableExpr(v) => {
+                    Ok( Expr::AssignExpr(Assign { name: v.name, value }))
+                }
+                _ => Err(ParseError { message: String::from("Invalid assignment target") })
+            }
+        } else {
+            Ok(expr)
+        }
+    }
+
+    fn equality(&mut self) -> Result<Expr, ParseError> {
         let mut expr: Expr = self.comparison()?;
 
         while self.match_token( &[TokenType::BangEqual, TokenType::EqualEqual]) {
@@ -112,7 +129,7 @@ impl Parser {
         return Ok(expr);
     }
 
-    fn comparison(&mut self) -> Result<Expr,ParseError> {
+    fn comparison(&mut self) -> Result<Expr, ParseError> {
         let mut expr = self.term()?;
 
         while self.match_token(&[TokenType::Greater, TokenType::GreaterEqual, TokenType::Less, TokenType::LessEqual]) {