The prevalence of asbestos bodies (AB) in sputum was studied in a group of 220 former or current asbestos workers, who came under observation because of a claim for compensation and who had, in most cases, high levels of exposure. Only one sputum specimen was obtained from each subject. The overall AB prevalence was 34%; it was 24.5% among workers exposed to chrysotile only, and 42% among workers also exposed to amphiboles, thus showing a statistically significant difference. No significant differences were found in AB prevalence either between current asbestos workers and former workers or between asbestosis cases and those without asbestosis. AB prevalence among current smokers was significantly lower than that observed among non-smokers and ex-smokers pooled together. The highest AB prevalence was found among currently exposed textile workers (65.7%), especially in male subjects (66.7%). As the exposure of these groups was heavy and included amphiboles, it may be concluded that although AB counts are highly specific they have low sensitivity.