Weanling albino rats were fed with either a control diet or one infested with Penicillium rubrum Stoll for a period of 30 days. At the end of the experimental period, determinations of haemoglobin, total proteins and transaminases were made in blood and tissues (liver, brain and kidney). The fungus was found to render the food toxic, resulting in liver and kidney damage. The toxicity of the fungus was also evidenced by poor live weight gains and organ weights.