In 1860, a Great Lakes ship captain migrated to Utah. This man is reported to have had a severe tremor during the last 20 years of his life. The present study is concerned with the characteristics and incidence of the tremor among four generations of his descendents, 24 of whom have been examined. Most reports on familial tremor describe the clinical findings observed in a few afflicted members from several unrelated families. Reliance is placed on the family history as presented by the patients for data about the incidence of this trait among other members of the family. As is illustrated in this report, such information may be unreliable as regards the frequency of occurrence of tremor in the progeny. Examination of the subjects usually was made in their homes, which lie within a radius of 40 miles of Salt Lake City. With the exception of the propositus (III-19), who