In 1973 Cohen et al reported a new syndrome in two siblings and an unrelated individual, consisting of obesity, mental retardation, hypotonia, limb abnormalities, and a characteristic craniofacial appearance. Since then no similar cases have appeared in the literature. This report firmly establishes the Cohen syndrome as a distinct clinical entity by presenting four additional patients, including a sibling pair of normal parents, suggesting autosomal recessive inheritance. One of our four patients has normal intelligence, indicating that mental deficiency is a variable feature of the syndrome.