The mechanical properties and the forming behavior of a dual phase sheet steel have been assessed. The effect of downgaging on forming properties was especially considered because of its importance in lighter weight, energy saving materials. A lower bound method has been used to determine the forming limit diagrams of the steel. Results have shown that the effect of sheet thickness on the stretch formability of the dual phase steel is comparable to some results published previously but not to others. The discrepancy could be due to variations in composition, processing and method used to determine the forming limit diagram of the steel. New formability curves and design guidelines for the steel have been obtained using a recently developed technique for the assessment of formability under simultaneous stretching and bending conditions.