Diabetes mellitus evoked by streptozotocine in rats is associated with the oxidative stress. We examined the effect of Schiff's base 2,5-dihydroxybenzaldehyde with a well-known antidiabetic drug aminoguanidine, 2,5-dihydroxybenzilideneaminoguanidine (BAG) on the production of markers of oxidative stress such as 4-hydroxy-2-nonenal (4HNE) and conjugated dienes in diabetic rats. BAG administration did not affect glucose level in diabetic rats but significantly decreased the production of 4HNE and conjugated dienes. On the other hand, BAG caused the elevation of conjugated dienes and an insignificant increase of 4HNE levels in the control animals.