OBJECTIVES: To assess utilization and prescribing patterns of antidiabetics in Taiwan. METHODS: This cross-sectional study used the Taiwanese Diabetic Pay-for-performance Register to extract a diabetic outpatient claim dataset from the National Health Insurance reimbursement data. Adult diabetic patients with at least one antidiabetic prescription during 2004 to 2008 were indentified and prescription details were collected. Antidiabetic drugs were stratified by into injection (insulin) and five chemical groups of oral drugs. Pattern of antidiabetic combination was categorised by both type and number of combined drugs. Frequency of different prescribing pattern was calculated and presented as annual prescribing rate and analyzed by Cochran-Armitage trend test to test a significant ascending or descending trends. All data was processed in SAS 9.1.3. RESULTS: Over 95% prescribing patterns was composed of monotherapy, combination of any two, and combination of any three antidiabetics with approximate 30%, 47%, and 18% annual prescription rate, respectively. The most frequent types of drugs within above three patterns included single sulfonylurea (SU1), combined one biguanide and one sulfonylurea (BG1+SU1), and combined one biguanide, one sulfonylurea and one thiazolidinedione (BG1+SU1+TZD1). Prescribing rates of SU1 (from 18.1% to 9.83%) and BG1+SU1 (from 37.6% to 34.46%) decreased over the study period (P<0.001), but BG1+SU1+TZD1 revealed an increasing trend (from 8.45% to 10.99%, P<0.001). Any prescribing pattern containing insulin presented an incremental annual prescribing rate, but the prescribing rates for those only consisted of oral antidiabetics declined over time. CONCLUSIONS: Antidiabetic prescribing patterns in Taiwan have changed and shifted from simple monotherapy to multiple combinations of newer drugs. Meanwhile, prescribing rates of single-use or combine-use insulin have also risen. It is necessary to further investigate the impacts of change prescription patterns on diabetic complications.