This study sought to determine the potential prophylactic and antioxidant effects of aminoguanidine in experimentally induced diabetes. Four groups of Wistar rats, each composed of ten rats, were used. Two groups served as control. In group 3, diabetes was induced by a single intraperitoneal injection of streptozotocin (65 mg kg-1). In group 4, diabetes was induced and treated with aminoguanidine (100 mg kg-1 daily) orally for 3 months. Levels of serum glucose, glutathione peroxidase, glutathione reductase and erythrocytes catalase were analyzed on day 90 of the experiment. Retinal and kidney specimens were examined histopathologically after sacrifice of the animals. A significant antioxidant effect of aminoguanidine and its prophylactic role in diabetic retinopathy and nephropathy were observed in experimental animals. U ovom radu ispitivano je potencijalno profilaktičko i antioksidativno djelovanje aminogvanidina u eksperimentalno induciranom dijabetesu. Ispitivanja su provedena na četiri skupine od 10 štakora. Dvije skupine bile su kontrolne skupine, u trećoj skupini dijabetes je induciran jednokratnom intraperitonealnom injekcijom streptozotocina 65 mg kg-1, a u četvrtoj dijabetes je induciran i tretiran aminogvanidinom 100 mg kg-1 dnevno, peroralno, tijekom 3 mjeseca. Devedesetog dana eksperimenta analizirane su koncentracije glukoze, glutation peroksidaze, glutation reduktaze i eritrocitne katalaze u serumu. Životinje su žrtvovane, a uzorci retine i bubrega ispitivani su histopatološki. Uočen je značajan antioksidativni učinak aminogvanidina i njegova profilaktička uloga u dijabetičkoj retinopatiji i nefropatiji.