The Japan Pharmaceutical Manufacturers Association. with the cooperation of the Japan Association of Contract Laboratories for Safety Evaluation. launched a collaborative study with 38 companies aimed at elucidating the correlation between histopathological/hematological findings and immune function. Seven substances were individually administered to Crj : CD (SD)IGS rats for 14 or 28 days. Their immunotoxicity was assessed by histopathology. hematology. plaque-forming cell assay. enzyme-linked immunosorbent assay of serum antibody to sheep red blood cells. and flow cytometry. Appropriate procedures for immunotoxicology evaluation of pharmaceuticals were considered.