A population-based case-control study of incident primary malignant brain tumours diagnosed during 1985 to 1989 in children aged 0 to 14 years was carried out in the coastal conurbation of New South Wales comprising Sydney, Wollongong and Newcastle in the period 1988 to 1990. Personal interviews were conducted using a structured questionnaire with mothers of 82 cases and 164 control children individually matched to the cases by sex and age. Among the hypotheses being examined were those related to exposure to parental tobacco smoke, N-nitroso compounds and possible protection from sources of vitamin C. No link was found with tobacco smoking by the mother before or during pregnancy. While exposure during pregnancy of the mother to tobacco smoke of the father appeared to double the risk of childhood brain tumours and a similar risk was found for father (but not mother) smoking before the index pregnancy, there was no "dose-response" and the increased risk was confined to data supplied by the mother (rather than the father himself). The risk of childhood brain tumours rose with reported increasing consumption, during pregnancy, of cured meats, which have high levels of N-nitroso compounds (or their precursors), and fell with rising consumption of vegetables. No association was found between the risk of childhood brain tumours and family history of epilepsy, cancer, or tumours of the nervous system, parental irradiation, previous miscarriage or procedures carried out during pregnancy, maternal consumption of antihistamines, barbiturates or diuretics, or maternal contact with cats or farm-life during pregnancy.