The frequency of cigarette, pipe and cigar smoking, and tobacco chewing among 77 patients with renal adenoma was compared with that among 134 control patients. Analysis of our data revealed among male patients with renal adenoma: (1) the proportion using tobacco was greater than among corresponding control patients. These differences (using the chi 2 test with continuity correction) were significantly greater among males with renal adenoma than among corresponding controls for: all types of tobacco use combined (at the 0.0005 level); smokers of more than ten cigarettes per day (at the 0.0005 level); pipe smokers, cigar smokers and tobacco chewers combined (at the 0.01 level); pipe smokers (not significant); cigar smokers (at the 0.005 level); and tobacco chewers (at the 0.05 level). (2) proportionally fewer male patients quit using tobacco among adenoma patients who had used tobacco than among control patients who had used tobacco (significant at the 0.01 level). (3) In the adenoma and control group of females the number of patients was not large enough for statistical analysis. (4) The estimated risk of males developing renal adenoma was increased with all forms of tobacco use.