Infertility is relative. Research into effective treatment must focus on couples with single, identifiable causes for their infertility, and must take into account the effect of chance and time on eventual success. Women with ovulatory infertility, who have no other subfertility factors, can expect normal conception rates when ovulation is restored. Unfortunately, there is no similar simple treatment for male infertility, although complicated and expensive treatment may help. Selection of the couples most likely to benefit from such help will result in the most cost-effective use of scarce resources. Knowledge of duration of infertility and the postcoital test result can help to identify those couples who have a reasonable chance of conception without treatment and those who have virtually no chance without it.