Background: Various oral hypoglycemic agents have already been administered to type-2 diabetic patients to normalize their plasma glucose concentrations but they have not had complete and sustained success. In recent years, bromocriptine has been tried with controversial results. In present study, the effect of bromocriptine on glycemic control was evaluated in obese type-2 diabetic patients. Methods: In a double-blind placebo-controlled clinical trial, 40 obese patients with type-2 diabetes (aged 32–70 years) were randomly allocated to the two treatment groups. The first group received bromocriptine (2.5 mg daily) for a total of 3 months. The second group received placebo. They had been uncontrolled on fixed doses of glibenclamide or its combination with metformin in the 3 months before enrolling in the study. The fasting plasma glucose (FPG) level and glycosylated hemoglobin (HbA<sub>1</sub>) were measured and body mass index (BMI) was calculated before and 1, 2 and 3 months after treatment. Results: The FPG level decreased in the bromocriptine-treated group from 10.59 ± 0.42 to 9.06 ± 0.41 mmol/l (mean ± SEM; p < 0.01), whereas in the placebo group it was not changed, 10.69 ± 0.52 and 10.6 ± 0.57 mmol/l, respectively. The HbA<sub>1</sub> concentration was reduced in the bromocriptine-treated group from 9.9 ± 0.3 to 9.5 ±0.2% (p = 0.06), whereas it increased in the placebo-treated group from 10.2 ± 0.3 to 11.3 ± 0.6% (p < 0.05). The differences in HbA<sub>1</sub> (1.8%, p < 0.01) and FPG (1.55 mmol/l, p < 0.05) levels between the bromocriptine and placebo groups at 3 months were significant. No changes in body weight or BMI occurred during the study in either placebo- or bromocriptine-treated group. Conclusion: The data further support the contention that bromocriptine improves glycemic control in obese type-2 diabetic patients, although the mechanism of action remains to be determined.