Whether alcohol and tobacco can be considered as risk factors for the occurrence of adenomas remains inconclusive. A case-control study was carried out to examine these factors while taking into account possible confounding factors. One hundred eighty-two patients with colorectal adenomas and similar numbers of hospital and population controls were compared as to intake of alcohol and various nutrients including smoking and drug intake. There was a positive association between cigarette smoking and adenoma risk compared with hospital controls, the RR being 2.3 (1.1-4.6). Overall alcohol intake was no risk factor in hospital controls, but drinking liquor was associated with an increased risk, the RR being 4.1 (1.3-13.4) and was especially marked in males [RR 10.2 (2.3-46.2)]. Compared with population controls, there was no increased RR associated with smoking or alcohol intake. None of the risk factors was positively associated with disease risk in those with small or large adenomas. These findings suggest that alcohol and tobacco play no major role in the formation or growth of adenomas.