Smoking behavior and weight change over a 5-year period were studied in 1,749 adult males of the Normative Aging Study. While men who quit smoking generally gained more weight than those in other smoking categories, 36% either lost weight or maintained the same weight after quitting. The major research focus was to predict the direction of weight change after smoking cessation. Among the characteristics most related to weight gain after quitting were heavier tar consumption, younger age, and leanness of body build. Conversely, traits related to weight loss were lighter smoking, older age, and stoutness of build.