DNA amplification and silver staining were used to identify Pneumocystis carinii in bronchoscopic lavage and induced sputum samples during 51 episodes of respiratory illness in 47 subjects with H IV infection. In 20 episodes, in which the clinical diagnosis was pneumocystis pneumonia (PCP), silver stain was positive in 14 lavage samples (70%) and 7 sputum samples (35%), whereas DNA amplification was positive in 19 lavage samples (95%) and 18 sputum samples (90%). DNA amplification was positive in only 1 of 31 patients without PCP (PCP developed in this patient within 10 weeks). DNA amplification on induced sputum offers a powerful technique for diagnosis of PCP. © 1991.