The objective was to evaluate the role of homologous intrauterine insemination compared with timed natural intercourse, both combined with ovulation induction, in the management of unexplained infertility. A total of 48 couples presenting at a large teaching hospital infertility clinic with unexplained infertility of at least 3 years duration comprised the main study group, and 36 couples with identical entry criteria but under the care of another clinician made up a parallel control group. A randomized design of treatment cycles with within-group and between-group controls was used. Couples in the main study group were treated with either homologous intra-uterine insemination or timed natural intercourse in gonadotrophin-releasing hormone analogue down-regulated cycles, in which ovulation was induced with human menopausal gonadotrophin and human chorionic gonadotrophin. Alternate cycles were monitored to enable optimum timing of natural intercourse provided within-group controls. Couples in the control group underwent timed homologous intravaginal artificial insemination. Cycle fecundity and pregnancy outcome in treated and control groups were monitored. Cycle fecundity of 0.11 in 85 ovulation-induced cycles was significantly higher than 0.02 in 62 within-group and 0.01 in 103 between-group control cycles. There was no difference in conception rates between homologous intra-uterine insemination and timed natural intercourse cycles with ovulation induction. Of the 11 established pregnancies in the ovulation induced group, nine delivered healthy babies (five singleton, three twin, one triplet) and two were ectopic. Results confirmed the value of active management for couples with long-standing unexplained infertility but failed to demonstrate any advantage of homologous intra-uterine insemination over ovulation induction alone.