Life threatening pneumonias after liver transplantation are often caused by opportunistic pathogens such as Legionella pneumophila, Pneumocystis carinii, Aspergillus species and cytomegalovirus (CMV). Due to the high incidence of morbidity and mortality caused by these pneumonias we reviewed 700 liver transplants for risk factors for the development of opportunistic pneumonia. Immunosuppression was commenced as either cyclosporin A- or tacrolimus-based protocols. In a subgroup of patients, splenectomy was performed simultaneously with liver transplantation ( n=57). Overall 60 opportunistic pneumonias occurred in 700 liver transplants. Using a stepwise logistic regression analysis, we found that OKT3 treatment and simultaneous splenectomy revealed a significantly increased risk for opportunistic pneumonia. Our study identified splenectomy as a major risk factor for the development of opportunistic pneumonia after liver transplantation. In these patients prophylactic protocols and early diagnosis may improve the long-term outcome.