The maximum pre-tax contribution dollar amount is set by law and adjusted for inflation annually. The 2009 pre-tax contribution limit is $16,500. If you are age 50 or older you may also make an additional catch-up contribution of $5,500 per year. Some plans may offer you the option to contribute on an after-tax basis which is not included in the $16,500 limit. Note that plans may restrict employee contributions to an amount less than $16,500, and may also choose not to permit catch-up contributions.