OBJECTIVES: Comparison of safety of intravenous metamizole, ketoprofen and paracetamol based on data from WHO Programme for International Drug Monitoring. METHODS: The data from countries participating in the World Health Organization Programme for International Drug Monitoring are collected and maintained, on behalf of the WHO, by the Uppsala Monitoring Centre, in the Vigibase. An analysis of data on adverse events (AE) of intravenous formulations of metamizole, ketoprofen and paracetamol, reported to Vigibase, from European countries since 1968 up to 29th January 2006 (ref: ER 132/2005), was performed. RESULTS: One thousand three hundred seventy one individual case reports of metamizole adverse events were registered in the Vigibase, compared to 367 and 69 for ketoprofen and paracetamol, respectively. Serious AE were reported in 29 metamizole cases, 47 – ketoprofen and none for paracetamol. There were 15 death cases registered for metamizole, 1 for ketoprofen and paracetamol. Hematologic disorders were reported in 187 metamizole cases, i.e. 6 and 31 times more common then for ketoprofen and paracetamol therapy, respectively. Most frequent AE reports for metamizole were: anaphylactic shock (79 cases versus 6 and 3 with ketoprofen and paracetamol, respectively), agranulocytosis (77 vs 3 vs 1), rash erythematous (63 vs 26 vs 3), hypotension (54 vs 6 vs 3), pruritus (53 vs 10 vs 1), rash (51 vs 17 vs 0), leucopenia (48 vs 6 vs 2) and circulatory failure (48 vs 5 vs 2). CONCLUSIONS Intravenous therapy with paracetamol is safer than with ketoprofen or metamizole, concerning total number of reported adverse events, number of reported serious adverse events and number of hematologic disorders. Death cases were reported 15 times more often with metamizole than with either paracetamol or ketoprofen.