The persistence and compliance of type 2 diabetic patients to different regimens of anti-hyperglycemic therapy were assessed retrospectively. The pharmacy claims from a pharmacy benefit management organization were analysed from the third quarter of 1996 to the fourth quarter of 1999. Of the 23,400 patients enrolled and initiating anti-diabetic therapy, 85% started treatment with monotherapy, 9.5% with insulin alone, 4.1% with polytherapy and 1.3% with insulin plus another therapy. Monotherapy patients were characterized as receiving metformin, sulfonylurea or another agent. For the 1-year follow-up period, 70.5% of the metformin patients, 75.3% of the sulfonylurea patients and 86.8% of the polytherapy patients underwent no regimen modification (except discontinuation). For the patients who had no modification of their medication regimen, persistence with sulfonylurea or metformin monotherapy was 65% greater than with polytherapy over a 1-year period. Compliance with sulfonylurea or metformin monotherapy was 45% greater than with polytherapy.