A puff of air administered to the face of 102 subjects (from 33 week's gestation on the first day of life to age 42 years) elicited a reflex swallow identical to a normal primary peristaltic sequence in 88. Subjects who responded were younger than 24 months of age or severely disabled neurologically; those who did not respond were older than 11 months and free of neurological abnormality. Response was variable between 11 and 24 months. This swallow response appears to be a clinically useful but previously unrecognised infant reflex.