We identified 60 pneumonitis cases in association with (peg)interferon a from the WHO database. In 33 cases the indication of (peg)interferon (and ribavirin) combination treatment was HCV. There were 16 (48%) males and 15 (45%) females in this cohort, with mean age of 53 years. We failed to retrieve cases that met the inclusion criteria from the Netherlands Pharmacovigilance Center and Drug-Induced Lung Diseases databases. Interferon monotherapy was used in three (9%) patients. Interferon a-2b in combination with ribavirin was used in eight patients (24%), while interferon a-2a in combination with ribavirin was used in a single case.