We retrospectively analysed adverse drug reactions (ADRs) associated with antibiotic therapy and reported over a 6-year period, from January 1995 to December 2000, in clinical notes of two Pulmonology Units of "Mater Domini" University Hospital and "Pugliese-Ciaccio" Hospital, both located in Catanzaro, Italy. Antibiotics were responsible for 92 (44.9%) out of 205 episodes of ADRs. In particular, 22 episodes (23.9%) were observed after penicillin G administration, 19 episodes (20.7%) following ceftazidime and cefotaxime administration, 16 episodes (17.4%) after therapy with ampicillin, and 35 reactions (38%) were further reported during treatments with other antibiotics. We determined that the drug-ADR relationship was certain in 63% of the reports; withdrawal of the suspected drug led to recovery in 95% of cases. In conclusion, this retrospective evaluation demonstrated that antibiotics are a common cause of ADRs in hospitalised patients and, therefore, drug surveillance can successfully identify targeted adverse events.