OBJECTIVES: To investigate whether employment in dry cleaning, and potential exposure to perchloroethylene (PCE), were associated with increased risk of carcinoma of the oral cavity and pharynx, larynx, oesophagus, and gastric cardia. METHODS: Two population based case-control studies were carried out. There were 491 cases of carcinoma of the oral cavity and pharynx, 235 of the larynx, and 404 of the oesophagus and gastric cardia. 724 controls were selected by random digit dialing. Personal interviews ascertained information on lifetime job histories, cigarette use, alcohol consumption, and other potential risk factors. The probability and level of exposure to PCE were estimated from the scientific literature. RESULTS: People who worked in dry cleaning tended to consume less alcohol and cigarettes than the general population. The adjusted odds ratio (OR) associated with ever having worked in dry cleaning was 1.6 (95% confidence interval (95% CI) = 0.6 to 4.4) for all cancer types together. The strongest associations were with laryngeal (OR 2.7; 95% CI 0.6 to 10.9) and oesophageal squamous cell carcinomas (OR 3.6; 95% CI 0.5 to 27.0). For laryngeal cancer, the relative risk increased with number of years employed in the dry cleaning industry (P = 0.14. The two cases of oesophageal squamous cell carcinomas had worked in dry cleaning for only a short time. Analyses of subsites showed higher risks for supraglottic laryngeal cancer (OR 5.7; 95% CI 1.0 to 32.1) and cancer of the tongue (OR 2.3; 95% CI 0.4 to 12.6). Analyses of exposure to PCE yielded similar results. CONCLUSIONS: These findings could easily be explained by chance; nevertheless, they are consistent with previous reports of excess risk of oesophageal, laryngeal, and tongue cancer, and suggest that previous studies of dry cleaners that could not control for alcohol and cigarette use may have underestimated the relative risks of such cancers.