We assessed the prevalence of hypoglycemic symptoms in patients (aged 40–65 yr) treated with oral hypoglycemic agents (OHAs) attending routine diabetes clinics at our hospital. Symptoms were experienced during the previous 6 mo in 41 of 203 (20.2%) patients treated with sulfonylureas but in none of the 16 patients treated with metformin alone. Hypoglycemic symptoms were experienced at least monthly in 5.9% and less frequently in 14.3% of patients. The prevalence of symptoms decreased with increasing duration of sulfonylurea administration (P < .01). Mean glycosylated hemoglobin and postprandial plasma glucose were significantly lower in patients reporting hypoglycemic symptoms than in those without symptoms (P < .001). The prevalence of hypoglycemic symptoms was significantly higher in patients treated with glyburide than in patients treated with gliclazide (P < .01) or chlorpropamide (P < .05). The prevalence of symptoms was higher in patients taking medications in addition to OHAs (P < .01). Ten (24%) of the patients who experienced hypoglycemic symptoms were taking drugs that may potentiate sulfonylureas.