The association between weight change over a 5-year period, the subsequent perception of health and the mortality during a 4-year follow-up period has been examined in a prospective study of 7735 middle-aged British men. There were 357 deaths from all causes. Self-assessment of health status was considered as a potential guide to whether weight loss was intended or involuntary. Irrespective of weight change those who reported poor or fair health had a more than two-fold increase in death rate compared to those who reported good or excellent health. Considerable weight gain (greater than 10%) was associated with high rates of cardiovascular disease regardless of health perception, although this was most marked in those who perceived poor or fair health. Moderate weight gain was of little importance except in those who regarded their health as poor or fair. Weight loss was associated with increased death rates from cancer regardless of health perception, although the rates were highest in those who perceived poor or fair health. This study emphasizes that weight loss is a potentially serious symptom even in men who report good health. Assessment of weight change and of perception of health status are both of value and could be used in standard health enquiries to monitor health status in individuals and the community.