Male weanling rats fed diets containing fermented and unfermented tannin-free sorghum meals naturally contaminated with traces of ochratoxin A, zearalenone, and an unidentified toxic substance developed anorexia. Mean changes in body weight over a 28-day feeding period for rats fed fermented and unfermented sorghum meal and ANCR casein diets of 8% protein were-2.8, + 13.8, and + 100.5 g, respectively. Rats fed fermented sorghum meal developed alopecia; hematological findings showed a decreased mean corpuscular volume, hypochromic microcytosis, balanced leukopenia, and hypoproteinuria. Histological findings showed testicular hypoplasia of the germinal epithelium and no mature spermatozoa. Necrosis and mineralization in Henle's loop were also observed. No damage was apparent to the liver, cerebellum, cerebrum, spleen, or adrenal glands.