diff --git a/src/parser.rs b/src/parser.rs
index dd13de5d..8c62aa08 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -154,6 +154,8 @@ pub enum Token {
     Fn,
     Break,
     Return,
+    PlusEquals,
+    MinusEquals,
     LexErr(LexError),
 }
 
@@ -436,13 +438,25 @@ impl<'a> TokenIterator<'a> {
                 '[' => return Some(Token::LSquare),
                 ']' => return Some(Token::RSquare),
                 '+' => {
-                    if self.last.is_next_unary() { return Some(Token::UnaryPlus) }
-                    else { return Some(Token::Plus) }
-                }
+                    return match self.char_stream.peek() {
+                        Some(&'=') => {
+                            self.char_stream.next();
+                            Some(Token::PlusEquals)
+                        },
+                        _ if self.last.is_next_unary() => Some(Token::UnaryPlus),
+                        _ => Some(Token::Plus),
+                    }
+                },
                 '-' => {
-                    if self.last.is_next_unary() { return Some(Token::UnaryMinus) }
-                    else { return Some(Token::Minus) }
-                }
+                    return match self.char_stream.peek() {
+                        Some(&'=') => {
+                            self.char_stream.next();
+                            Some(Token::MinusEquals)
+                        },
+                        _ if self.last.is_next_unary() => Some(Token::UnaryMinus),
+                        _ => Some(Token::Minus),
+                    }
+                },
                 '*' => return Some(Token::Multiply),
                 '/' => {
                     match self.char_stream.peek() {
@@ -544,7 +558,7 @@ impl<'a> TokenIterator<'a> {
 impl<'a> Iterator for TokenIterator<'a> {
     type Item = Token;
 
-    // TODO - perhaps this could be optimized to only keep track of last for operators?
+    // TODO - perhaps this could be optimized?
     fn next(&mut self) -> Option<Self::Item> {
         self.last = match self.inner_next() {
             Some(c) => c,
@@ -560,7 +574,9 @@ pub fn lex(input: &str) -> TokenIterator {
 
 fn get_precedence(token: &Token) -> i32 {
     match *token {
-        Token::Equals => 10,
+        Token::Equals
+        | Token::PlusEquals
+        | Token::MinusEquals => 10,
         Token::Or => 11,
         Token::And => 12,
         Token::LessThan
@@ -591,7 +607,7 @@ fn parse_call_expr<'a>(id: String,
                        input: &mut Peekable<TokenIterator<'a>>)
                        -> Result<Expr, ParseError> {
     let mut args = Vec::new();
- 
+
     if let Some(&Token::RParen) = input.peek() {
         input.next();
         return Ok(Expr::FnCall(id, args));
@@ -756,6 +772,20 @@ fn parse_binop<'a>(input: &mut Peekable<TokenIterator<'a>>,
                 Token::Multiply => Expr::FnCall("*".to_string(), vec![lhs_curr, rhs]),
                 Token::Divide => Expr::FnCall("/".to_string(), vec![lhs_curr, rhs]),
                 Token::Equals => Expr::Assignment(Box::new(lhs_curr), Box::new(rhs)),
+                Token::PlusEquals  => {
+                    let lhs_copy = lhs_curr.clone();
+                    Expr::Assignment(
+                        Box::new(lhs_curr),
+                        Box::new(Expr::FnCall("+".to_string(), vec![lhs_copy, rhs]))
+                    )
+                },
+                Token::MinusEquals  => {
+                    let lhs_copy = lhs_curr.clone();
+                    Expr::Assignment(
+                        Box::new(lhs_curr),
+                        Box::new(Expr::FnCall("-".to_string(), vec![lhs_copy, rhs]))
+                    )
+                },
                 Token::Period => Expr::Dot(Box::new(lhs_curr), Box::new(rhs)),
                 Token::EqualTo => Expr::FnCall("==".to_string(), vec![lhs_curr, rhs]),
                 Token::NotEqualTo => Expr::FnCall("!=".to_string(), vec![lhs_curr, rhs]),
diff --git a/src/tests.rs b/src/tests.rs
index 98f75862..cd0b1e53 100644
--- a/src/tests.rs
+++ b/src/tests.rs
@@ -457,3 +457,37 @@ fn test_loop() {
 		").unwrap()
 	)
 }
+
+#[test]
+fn test_increment() {
+    let mut engine = Engine::new();
+
+    if let Ok(result) = engine.eval::<i64>("let x = 1; x += 2; x") {
+        assert_eq!(result, 3);
+    } else {
+        assert!(false);
+    }
+
+    if let Ok(result) = engine.eval::<String>("let s = \"test\"; s += \"ing\"; s") {
+        assert_eq!(result, "testing".to_owned());
+    } else {
+        assert!(false);
+    }
+}
+
+#[test]
+fn test_decrement() {
+    let mut engine = Engine::new();
+
+    if let Ok(result) = engine.eval::<i64>("let x = 10; x -= 7; x") {
+        assert_eq!(result, 3);
+    } else {
+        assert!(false);
+    }
+
+    if let Ok(_) = engine.eval::<String>("let s = \"test\"; s -= \"ing\"; s") {
+        assert!(false);
+    } else {
+        assert!(true);
+    }
+}