We studied the prognostic value of sperm characteristics for the outcome of intra-uterine insemination with partner sperm (IUIPS). A total of 712 cycles of IUIPS following induction of ovulation with gonadotrophin (hMG/ hCG) for 277 sterile couples attending the assisted reproductive technology centre of Poissy Hospital (78300-France) between January 1991 and December 1994 was studied retrospectively Ninety-two clinical pregnancies were obtained giving an overall rate of 12,9 % per cycle, None of the characteristics of the sperm as assessed initially correlated with outcome, In contrast, the number of motile spermatozoa given (n) affected outcome : for n < 1 x 10(6) the pregnancy rate was 2 %; for n = 5 to 8 x 10(6) the rate was 19 %, However, for greater than or equal to 8 x 10(6) the proportion of biochemical pregnancies and miscarriages was 40 % which was significantly higher than for smaller concentration. The resort of IVF following 4 IUIPS failures leads to a pregnancy rate per cycle of only 6,7 %.