Aluminum alloy sheets of 2010-T4 of 0.831 mm and 2.590 mm thicknesses and 6111-T4 of 1.029 mm thickness were tested to determine the Forming Limit Diagrams (FLDs). The forming limit curves were obtained from both rolling and transverse samples. Due to the large scatter observed in the experimental data, exact identification of the forming limit based on incipient necking was not an easy task. Two alternate methods of determining the equivalent FLDs were explored and tested. The resulting forming limit curves based on the two methods are reasonably consistent with trends indicated by previous forming limit diagram determinations.