Branched chain amino acids (BCAA) are known to exert insulinogenic effect. Whether this effect is mediated by incretins (GLP-1, GIP) is not known. The aim of the study was to show incretin effect of BCAA, i.e. whether the oral administration of BCAA elicits higher insulin and incretin response when compared with IV route of the same dose of BCAA. Eighteen healthy, male subjects participated in three tests: IV application of BCAA solution (30.7±1.1 g of BCAA, IV BCAA) second was oral ingestion of BCAA capsules in the same dose (ORAL BCAA) and third experiment was oral placebo (PLACEBO). Glucose, insulin, GLP-1, GIP, valine, leucine and isoleucine levels were measured at time interval for up to 4 h.