Pneumocystis jirovecii is an opportunistic pathogen causing life-threatening pneumonia in immunosuppressed patients. The number of non-HIV immunosuppressed patients at risk for Pneumocystis pneumonia is rapidly growing. In contrast to HIV patients, there are no guidelines for Pneumocystis prophylaxis in other immunocompromised hosts. A detailed analysis of current literature data allowed us hereby to define the type of immunocompromised patients for whom evidence suggests a benefit for PCP prophylaxis.