Proven Pneumocystis carinii pneumonia (PCP) occurred in 8 (5.2%) of 154 adult liver transplant recipients between January 1986 and December 1992. The interval between transplantation and PCP ranged from 69 to 131 days with a mean of 95 days (SD 20 days). The PaO2 breathing room air at diagnosis ranged from 40 mmHg to 75 mmHg with a mean of 59.6 mmhg (SD 13 mmHg). Bronchial washings taken at bronchoscopy stained positively for Pneumocystis carinii and confirmed the diagnosis. Transbronchial biopsy was unnecessary for diagnosis. One patient died from PCP while the remainder recovered. Patients transplanted immediately before the index patients served as controls. Patients who developed PCP had more episodes of rejection (p < 0.05), received more OKT3 (p < 0.05), and were receiving more prednisone (p < 0.05) than controls. They also had lower levels of albumin (p < 0.01), and higher levels of alkaline phosphatase (p < 0.05), alanine (p < 0.01), and aspartate aminotransferase (p < 0.001), and gamma-glutamyltranspeptidase (p < 0.02). This study raises the possibility of selecting patients at risk of PCP for chemoprophylaxis.