Several clinical parameters have been studied in a sample of 211 essential hypertensives in order to determine their usefulness as predictors of therapeutic response. One hundred and twenty-four patients (58.8%) achieved normotension with monotherapy, whereas 87 hypertensives (41.2%) needed two or more drugs to control their BP values. Patients who required a combination of drugs exhibited higher levels of systolic and diastolic BP, higher frequency of acute severe hypertension before the beginning of treatment, a more advanced stage of hypertension, and higher plasma aldosterone levels when they were compared with those controlled with a single drug. Likewise, previous cardiovascular complications related to hypertension, enlargement of cardiac silhouette on chest x-ray films and left ventricular hypertrophy were more frequent in the former. By means of a logistic regression analysis, these last three parameters showed a significant relationship with the number of required drugs. We conclude that hypertensives exhibiting this clinical profile have a higher probability of requiring a combination of drugs in the pharmacological treatment of essential hypertension.