INTRODUCTION Frequent use of modern imaging methods (such as ultrasound, CT and MRI) results in high incidence of accidentally discovered adrenal mass. Adrenal incidentalomas are accidentally discovered adrenal tumors by imaging methods without any prior suspicion of adrenal disease. Some studies have shown decreased insulin sensitivity in patients with adrenal incidentaloma. OBJECTIVE The objective of our study was to assess the insulin sensitivity in patients with adrenal incidentalom a. METHOD A total of 22 patients with accidentally discovered adrenal mass confirmed by CT/MRI were evaluated in our study. Average age was 53.31 +/- 26.5 years and average BMI 25.84 +/- 3.65 kg/m2. Control group consisted of 33 healthy subjects. Insulin sensitivity was assessed by short ITT (insulin tolerance test). Blood samples were taken before, 3, 6, 9, 12, 15, 20 and 30 minutes after i.v. bolus of regular insulin (0.05 IU/kg BW). Glycemia was determined by glucose oxidase method. Statistical analysis was done by ANCOVA, using BMI as covariate. RESULTS Our results showed significantly lower insulin sensitivity in patients with adrenal incidentalomas comparing to the control group (4.95 +/- 0.58 vs. 6.62 +/- 0.47, p=0.015). CONCLUSION Our patients with adrenal incidentalomas manifested lower insulin sensitivity what suggested further follow up and assessment of insulin sensitivity during endocrine evaluation of these patients.