A deaf-mute boy of 14 years, who was examined owing to his poor progress in the special school for the deaf-mute, proved to be one of a twin. Both boys were born 6 weeks before the normal term by breach presentation at the end of an uncomplicated pregnancy. There was one placenta. The mother had noticed A's deafness when he was 11 weeks old, as he did not react to street noises as his brother did. The twin brother B is deaf in the right ear; he attends the secondary school and his performance is average.