In Germany, reports on adverse drug reactions (ADRs) are centrally collected and analyzed by the Federal Institute for Drugs and Medical Devices (BfArM). During routine analysis of ADR reports related to the antiobesity drug sibutramine, we repeatedly observed descriptions of its label*-inconsistent use (*European Summary of Product Characteristics (SmPC)). In order to quantify this observation, we analyzed all sibutramine-related ADR reports received by the BfArM so far. Using the same data source, we further analyzed the effect of a Dear Doctor Letter (DDL) which was distributed in 2002 in order to reinforce the label-consistent use of sibutramine. Out of a total of 170 identified reports, 104 were considered as suitable for further analysis. Of these, applying a catalogue of 24 SmPC-derived criteria, 34% (35 reports) contained information indicative of label-inconsistent use. The individual SmPC-criteria most often violated were (% of total analyzed reports): the recommended starting dose of 10 mg/day (9%), the body mass index (BMI)-related threshold permitting drug therapy (6%), and the contraindicated "history of drug abuse" (6%). The DDL was ineffective. The observed percentage of ADR reports, indicating a label-inconsistent use of sibutramine, is considered a signal for a therapeutic risk. This signal should be addressed in a drug utilization study investigating the use of sibutramine by means of a representative patient sample.