Abstract: The purpose of this study was to evaluate the toxicology of crude xylanase enzymes prepared from T. aurantiacus SL16W in male Albino rats. Sixty rats aged 6 weeks old were randomly distributed into 4 groups of 15 rats. The 1st group was the untreated control while the 2nd (400 U), 3rd (2000 U) and 4th (4000 U) groups received the crude xylanase enzyme at dose levels of 400, 2000 and 4000 unit/kg body weight/day, respectively. After treatmemt body weight, organ weight, hematology and plasma chemistry were examined. The results indicated that oral force-feeding of the crude xylanase enzyme did not affect the body and organ weight of the rats. Hemoglobin values in the 2000 U group and hematocrit values in the 2000 U group were slightly decreased compared to the control group. The levels of Blood Urea Nitrogen (BUN), creatinine, aspartate Aminotransferase (AST) and alanine Aminotransferase (ALP) were not significantly different between the groups except that the ALT of the 200 U was significantly lower than the control group.