Clinical and electrophysiologic features of an infant with stiff-baby syndrome were studied; his father, uncle, and paternal grandmother suffered from a similar disorder. They all had a similar facial appearance during infancy (an alert, frightened, tense look) and a tendency to vomit because of hiatal hernias. The condition is benign but causes anxiety and, later, embarrassment as affected adults suddenly fall when stumbling or startled. We suggest that the condition be called hereditary stiff-baby syndrome. The family history is suggestive of autosomal dominant inheritance.