Respiratory specimens were prospectively examined for Pneumocystis carinii from 53 patients. The majority of specimens were comprised of expectorated sputum, induced sputum, broncho-alveolar lavage (BAL), and tracheal aspirates. In only four patients Pneumocystis carinii (P. carinii) was detected. All the samples were produced by broncho-alveolar lavage. Candida spp and Aspergillus spp were also identified in a small number of patients. Acid-fast-bacilli were not detected in any of the cases under study. There were no sex-related differences in distribution. The present prospective study was undertaken in order to determine P. carinii infections in human immunodeficiency virus (HIV) seropositive and seronegative individuals. Expectorated sputum samples were probably the major limiting factor in low positivity for detection of P. carinii and study of BAL specimens would be more useful for better results.