Hormonal detection of urinary pregnanediol-3 alpha-glucuronide proved an effective method of monitoring the progress of oestrous cycles in the blackbuck; observation of sexual behaviour in a vasectomized male was, however, a more practical procedure. Good correlation was observed between the occurrence of minimal pregnanediol concentrations in females and the maximal behavioural response by the male. On the basis of intervals between periods of behaviourally detected oestrus, a mean cycle length of 16.9 days (+/- 0.62, s.e.m.) was derived from 12 cycles (4 animals). Eleven females were inseminated in this study, 8 with freshly collected semen and 3 with frozen semen; 6 calves were obtained, 1 after the use of frozen semen. Pregnancy was monitored by measurements of pregnanediol-3 alpha-glucuronide excretion and by ultrasound scanning. The mean interval between insemination and parturition was 183.3 days inclusive, ranging from 182 to 186 days.