Summary There is an association between dairy product consumption and the incidence of testicular cancer in different countries. To test the hypothesis that milk and dairy products are risk factors, a case-control study was performed in East Anglia, UK. All the cases were men with testicular cancer and for each of the 200 cases there were four controls, two cancer controls and two population controls. The response rate of those eligible subjects who received a questionnaire was: cases 73%, cancer controls 65% and population controls 57%. All responding subjects completed a dietary questionnaire including questions on current and adolescent milk, dairy product and fruit and vegetable consumption. The answers were corroborated when possible by the subjects' mothers using a separate questionnaire. MethodsThe hypothesis was tested by a case -control study. Adolescence was chosen because this is the period when the incidence of testis cancer starts to rise sharply and testicular activity, as indicated by the blood levels of testosterone, is rising most quickly, reaching a peak around age 20 (Vermeulen et al., 1971;Stearns et al., 1974 As it is obviously difficult for adults to remember their food consumption in adolescence, thereby introducing scope for recall bias, subjects were asked:(1) about current consumption, which they then used as a reference for consumption in adolescence; (2) to send a questionnaire to their mothers (if possible).