Syngeneic male skin grafts are tolerated by some multiparous mice. Multiparous female B6.EiJ (▪, n = 9), B6.A2 (▴, n = 6), HW80 (•, n = 10), and naive B6.EiJ (□, n = 12) mice were grafted with syngeneic male tail skin. Survival of skin grafts was monitored every 2 to 3 days.