Abstract: The sub-acute toxicity studies of 5-Hydroxy-2 (Hydroxy-methyl) 4H- pyran-4 one, a metabolite of Aspergillus fumigatus was carried out in rats. The compound was administered at a dose of 300 μg/rat/day for 21 days. The gross general observation such as changes of body weight, hematological profiles, biochemical parameters of blood and the histopathology of the liver, kidney, heart, lung, spleen were investigated both in control and experimental rats. The body weights of the rats were slightly increased. The change of hematological and biochemical parameters were statistically insignificant. No abnormalities were found in the histopathology of the liver, kidney, heart, lung and spleen in the experimental group of rats when compared with control group of rats.