Histopathologic evidence in recent literature suggests that habitual, heavy marijuana smoking causes changes in the bronchial airways similar to changes seen in older, habitual cigarette smokers. The cytologic effects of marijuana smoking on the bronchial airways were investigated utilizing a quantitative analysis of sputum. Levels of macrophages (pigmented and nonpigmented), neutrophils, mucus, mucous spirals, and columnar and benign metaplastic cells were measured. The presence or absence of dysplasia, "purse" cells, eosinophils, reactive bronchial lining cells, and benign bronchial hyperplasia was noted. Results were compared across three groups of 25 subjects each: never cigarette or marijuana smokers: marijuana only smokers: and in cigarette only smokers. Results indicate that cytomorphologic changes observed in habitual marijuana smokers are similar to changes observed in tobacco smokers and much different than those observed in nonsmokers. These cytologic findings are similar to those described in other studies from specimens obtained at bronchoscopy.