SummaryOver a 4‐year period, 259 men were investigated for primary (86%) or secondary (14%) infertility. Some 3–5 years after the initial investigation, 200 of these men were followed up and the conception rate of their partners assessed. Their age at investigation, total testicular volume, sperm density, sperm motility, percentage morphologically normal sperm and the duration of infertility all gave information about the prospects of conception. A stepwise discriminant analysis showed that the age of the men at investigation, sperm density, sperm motility and the duration of infertility all had a strong discriminant bearing on future conception. A score based on these four variables for the estimation of prognosis in ‘subfertile’ men has been devised and would seem to be clinically