We present three patients with the Coffin-Lowry syndrome, two males aged 21 years and 14 months respectively, and an unrelated girl aged 11 years. In the male patients the features at different ages are reviewed. Besides, we describe the pertinent features of their affected female relatives. The contribution of the family history to making the diagnosis is stressed. The isolated female proband is much more severely affected than the female relatives of the male probands, demonstrating that the clinical picture in female carriers of Coffin-Lowry syndrome can vary considerably. The differential diagnosis of Coffin-Lowry syndrome will be discussed shortly.