Anaerobic sarcinae were quantitatively isolated from suspensions of faeces heated at 70°C for 10 min. by plating on meat infusion agar containing lactose, neutral red and egg-yolk and incubating anaerobically at 37°C. Sarcina ventriculi was found in numbers up to 108 per g in faeces from 75 out of 106 healthy human adults living on vegetarian diets, but the organism occurred in the faeces of only 2 out of 123 people living on diets containing animal products. The identification and distribution of the organism are discussed and it is concluded that diet influences the colonisation of sarcinae in the human intestine.