Media examined for enumeration of mouse fecal flora populations were KF Streptococcus agar (KF), Mannitol salt agar (MS), Baird-Parker agar (BP), Brucella blood agar (BA), Wilkins-Chalgren blood agar (WC), Brucella blood agar + vancomycin and kanamycin (VK), Wilkins-Chalgren blood agar + nalidixic acid and vancomycin (NAV), Wilkins-Chalgren blood agar + nalidixic acid and Tween 80 (NAT), LBS agar, and Rogosa agar. Representative colonies from each medium were isolated for Gram morphology and species identification using API systems. Mannitol salt agar was more selective than Baird-Parker agar for staphylococci. VK agar appeared to be more selective for obligately anaerobic Gram negative bacilli than NAV agar. Higher counts of Gram positive rods were obtained with Rogosa agar than with LBS agar.