The strain aging behavior of five microalloyed steels was studied using a variety of straining, aging and stress relieving cycles. The materials studied were pressure vessel steels ASTM A737 Grade B and A737 Grade C, and structural steels ASTM A588 Grade A, A588 Grade B and ASTM A572 Grade 50, Type 2.The A737 Grade B and Grade C steels were tested in the normalized condition while the A588 Grades A and B and the A572 Grade 50 Type 2 steel were tested in both the as-rolled and normalized condition.The steels were cold strained in tension 2, 5 or 10% and were aged at 260 or 370C (500 or 700F) for 10 hr. Strained and aged specimens were stress relieved for 2 and 10 hr at 620C (1150F). Transverse mechanical properties were measured for the as treated, strained, aged and stress relieved steels.