Most case-control studies of colorectal cancer have shown a positive association with energy intake. In contrast studies which have considered physical activity have found the most active to have a lower risk of colonic cancer and obesity appears to be no more than weakly related to colorectal cancer. We therefore compared energy intake determined by a diet history interview, self-reported height and weight, together with measures of lifetime job activity levels and leisure activity in the year prior to interview in 147 cases with colorectal adenomas and two control groups (a) 153 age-sex matched FOB-negative subjects (b) 176 FOB-positive subjects in whom no adenoma or carcinoma was found. Unconditional logistic regression was used to estimate relative risks (RR) and 95% confidence intervals () adjusted for age, sex and social class. No association with weight or body mass index was found. The only association with physical activity found with both control groups was an inverse association with running or cycling for half an hour continuously at least once a week RR 0.46 (0.2-1.3) compared with control group (a), and RR = 0.32 (0.1-0.8) compared with (b), but few subjects engaged in such activity. There was an inverse association with energy intake (trend chi 2 = 5.3, P < 0.025) in the comparison with control group (a) only, a finding which is consistent with those of two previous studies of asymptomatic adenoma.