An evaluation strategy under which an expression is evaluated by repeatedly evaluating its leftmost innermost redex. This means that a function's arguments are evaluated before the function is applied. This method will not terminate if a function is given a non-terminating expression as an argument even if the function is not strict in that argument. Also known as call-by-value since the values of arguments are passed rather than their names. This is the evaluation strategy used by ML, Scheme, Hope and most procedural languages such as C and Pascal.

See also normal order reduction, parallel reduction.