OBJECTIVES: Opioids are the mainstay of therapy for patients with moderate to severe pain. Mandatory generic substitution exists in South Africa, unless otherwise indicated by the prescriber or if the patient refuses. Few studies have been conducted in South Africa analysing the prescribing patterns and cost of opioid analgesics. METHODS: A retrospective, cross-sectional drug utilisation study was conducted on prescription data of a medical insurance scheme administrator in South Africa for 2011. The database contained 2 298 312 records for medicine, medical devices and procedures. RESULTS: A total of 97 491 analgesics were dispensed to 31 854 patients during the year. Within ATC category N02, opioids (NO2A) accounted for 26.55% of analgesic prescriptions at a cost of R1 071 230.14. A total of 9 793 patients were prescribed 25 888 opioid analgesics. The average age of patients was 41.50 (SD=16.61) years. Female patients were slightly younger (average age: 40.69 (SD=17.05) years) than male patients (average age: 42.32 (SD=16.09) years). Nine different active ingredients and two combination products were prescribed. Tramadol, an atypical opioid, was the most often prescribed (68.11%), followed by pethidine (14.39%) and morphine (8.38%). The average cost per prescription was R41.38 (SD=R69.29). Fentanyl had the highest average cost per prescription (R454.43), and pethidine the lowest (R8.53). Overall, the average cost for an originator product was R56.25 and for a generic product R28.95. Tramadol accounted for 68.11% of prescriptions and 80.40% of cost. Tramadol had the most most branded generic equivalents on the market (7), yet only had 42.89% generic prescribing. Most prescriptions were issued by private hospitals (62.89%), followed by pharmacies (24.41%) and general medical practices (12.16%). Only 35.48% of the products were prescribed on a chronic basis. CONCLUSIONS: Tramadol dominated opioid prescribing. The study confirmed price differences for opioid analgesics between branded generics and originator products.