In the time period 1988-2000, a case-case study on environmental factors and lung cancer risk was conducted in Montevideo, Uruguay. This study was designed in order the establish possible differences between squamous cell carcinomas (SCC) and small cell carcinomas (SCLC) of the lung in relation to tobacco smoking. Three hundred and ninety one (391) patients with small cell carcinoma were compared with 1187 patients with squamous cell carcinoma. Regarding sex, the study included a small number of women (26 with SCLC and 20 with SCC). SCLC was associated with higher risks for smoking status, smoking intensity and cumulative exposure to tobacco smoking when compared with SCC. These three tobacco variables were significantly different between both cell types in men. Smoking duration was significantly higher among SCLC compared with SCC only in women. With decreasing age at starting to smoke, the proportion of SCLC increases at the expense of SCC. Finally, types of tobacco and cigarette were not different between cell types in both sexes. It should be noted that these tobacco variables were not associated with increased risks among SCC, when this cell type was compared with SCLC. These results suggests that SCLC display the strongest relation with tobacco smoking than SCC.