OBJECTIVES: Cost evaluation of prescribing patterns for citalopram and escitalopram in two outpatient settings. METHODS: Prescribing patterns of citalopram and its enantiomer escitalopram were studied separately in 2 clinical settings from January 2000 to March 2007. Setting 1 included all prescriptions from GPs and specialists installed in the canton of Geneva. All filled prescriptions are systematically recorded by a unique pharmacist's organisation (OFAC invoice office), which represents 92% of all prescriptions filled in the canton Geneva (around 500,000 inhabitants). Setting 2 included all prescriptions provided by the Geneva University Hospitals to outpatients. RESULTS: Despite the commercialisation of citalopram generics as of October 2002, and despite the marketing of escitalopram as of March 2002, the total amount of citalopram prescribed remained constant from 2000 to 2007. The prescription of escitalopram increased from 2002 onwards. In January 2007, the volume of prescription in setting 1 was 12 Daily Defined Doses per 1,000 inhabitants (DDD/1,000) for citalopram and 8 DDD/1,000 for escitalopram. In setting 2, the DDD/1,000 was around 1 for both citalopram and escitalopram. Around 76% of citalopram prescriptions were dispensed as generics in both settings. Considering all available dosages and conditioning forms in Switzerland, proprietary citalopram is 1 Euro per tablet more expensive than generic citalopram; escitalopram is 0.8 to 1 Euro per tablet more expensive than generic citalopram, depending on the size of the package. From April 2006 to March 2007, had only generic citalopram been prescribed instead of escitalopram, the total estimated savings would have been 0.95 million Euros. CONCLUSION: Prescription of generic citalopram instead of escitalopram could lead to major savings.