In living donor kidney transplantation there are disproportionately more female-to-male donations and fewer male-to-female donations. Given the rapid increase in living donor transplantation, we studied gender demographics and outcomes of these transplants. We analyzed living donor kidney transplants in the Scientific Registry of Transplant Recipients (SRTR) database between 1990 and 1999. There were 30 258 living donor transplants [26 510 (87%) biologically related; 2367 (8%) spousal; 1381 (5%) nonspousal unrelated]. Females comprised 68% of spousal and 56% of related and unrelated nonspousal donors (p < 0.0001). The distributions of gender pairings in nonspousal groups (related and unrelated) were significantly imbalanced (p < 0.0001). Opposite-sex pairs demonstrated more female-to-male donations among living related (64%, p < 0.0001), unrelated nonspousal (65%, p < 0.0001), and spousal pairs (68%). The higher incidence of end-stage renal disease among males and the slight predominance of females in the general population did not explain these gender disparities. Male recipients of male donor kidneys demonstrated significantly higher graft survival than other combinations (p < 0.006). Gender disparities in living donor transplantation result from a higher proportion of wife-to-husband donations and disproportionate female-to-male donations among biological relatives and unrelated pairs. There appears to be a graft survival advantage for male recipients of male donor kidneys.