A study of 537 patients referred to the Cardiac Work Evaluation Unit of Boston during the 5-year period from 1955 to 1960 has been undertaken. The present report concerns the 375 individuals with coronary or hypertensive heart disease evaluated during the period of study.Of the total number, 76 were considered unemployable and 299 (80 per cent) employable. Of the employable, 64 (21 per cent) are known to have died subsequently. Of those for whom some follow-up was obtained, 82 per cent returned to work or continued working after initial evaluation. When last known, 64 per cent of those still alive were still working. The mean duration of follow-up for this series was 4.5 years.Consideration of the factors that may influence the subsequent employment experience indicated that successful employment was significantly more frequent for subjects below the age of 50, with favorable current cardiac classification (IIB or better), with apparently good motivation, or after a period of unemployment less than 1 year, than for patients inwhom any of these factors was unfavorable. Certain specific medical factors, such as heart size, history of previous myocardial infarctions, and blood pressure, had a less constant relation to subsequent employment, though they did have some relation to the medical prognosis.There was no indication in the present study that employment influenced the mortality statistics.