Streptozotocin (STZ) is a naturally occurring nitrosoamide used extensively to produce diabetes in experimental animals. Since streptozotocin reportedly decrease deformability of red blood cells (RBC), we sought to investigate its potential toxicity at RBC. In addition to elevation blood glucose, 100mg/kg iv streptozotocin caused significant RBC hemolysis in female Sprague-Dawley at 48 hrs post treatment. Streptozotocin induced hemolysis was found to be dose and time-dependent` complete hemolysis required a relatively high streptozotocin concentration (500 mM, 4 hrs incubation), which is much more than in vivo dose.