The effect of neurotropin (NSP) in combination with streptozotocin (STZ) and cyclophosphamide (CY) on blood glucose and pancreatic histopathology on day 7 and day 14 after the initiation of the treatment was studied in C57Bl/6 male mice. STZ (40 mg/kg) and NSP (1 mg/kg) were applied intraperitoneally on five consecutive days and CY (150 mg/kg)--twice on day 1 and day 3. In single B cells dilatation of the endoplasmic reticulum was found. On day 7 in proximity to some endocrine cells in the mice treated with STZ, STZ + CY + NSP and STZ + CY macrophages were observed. On day 14 lymphocytic infiltration of the islets was demonstrated only in the groups of mice injected with STZ, STZ + CY while in the group treated with the combination STZ + CY + NSP no infiltration was seen. All experimental groups showed no biochemical evidence for hyperglycemia probably due to the mild destruction of a small number of B cells. The results indicate that NSP might possess a restorative action on insulitis induced by multiple low dose streptozotocin administration in mice.