Body mass index, alcohol and salt consumption, and parental history of hypertension were examined as possible predictors of the development of essential hypertension in 1,031 persons, ages 30-49 years at entry, with documented normotension followed by documented hypertension after a mean interval of 6 years. In a comparison with 1,031 matched persistently normotensive persons initial body mass index and percentage increase in body mass index were each predictive of hypertension. Consumption of three or more alcoholic drinks a day at baseline was also predictive, more so if this level of intake persisted than if it diminished. Heavy salt intake as crudely estimated at baseline by one question was also associated with the development of hypertension. Parental history of hypertension was also predictive, more so for hypertension in the mother than for hypertension in the father, and the association was apparent only in female subjects. These characteristics at baseline showed independent associations with subsequent hypertension in multivariate analysis. When follow-up data were included in the multivariate analysis, alcohol consumption at the hypertensive examination was much more strongly related than at the baseline examination, suggesting a short-term effect, and heavy salt consumption was no longer predictive, possibly because of a marked loss of subjects due to missing follow-up data. This large study confirms longitudinally the importance of obesity, weight gain during adulthood, alcohol, family history, and, to some extent, salt as predictive and possibly causal factors for essential hypertension.