We present the clinical findings and follow-up data of four female children with Cohen syndrome, two sisters and one pair of dizygotic female twins. The most characteristic findings from birth on were as follows: 1. Low-normal growth parameters at birth. 2. Mild hypotonia and evidence of progressive microcephaly with narrow forehead in the first year of life. 3. Neutropenia was present from the beginning, remained unchanged over the years and is not associated with higher susceptibility to infections. 4. Autistic behavior and severe psychomotor retardation up to the age of 2 years. At that age the ocular anomalies with high-grade myopia and chorioretinal dystrophy were diagnosed. Correction of the myopia resulted in a marked catch-up in psychomotor development. 5. After the age of 6 years facial stigmata became more evident with short philtrum of the upper lip and broad and large upper incisors. 6. Tendency to truncular obesity with rest hypotonia and poor muscle development after the ages of 6 to 8 years. The clinical findings and follow-up data in the present four children with Cohen syndrome illustrate that the diagnosis of Cohen syndrome in infancy is very difficult.