Preliminary results are presented for the first 13 patients to complete an ongoing crossover study comparing the effects of prazosin and propranolol on blood pressure control, in which blood lipid profiles were monitored. The study population consisted predominantly of white men (mean age, 67.5 years) with mild-to-moderate hypertension and coexisting hypercholesterolemia (mean plasma cholesterol level, 244 mg/dl). Both agents resulted in statistically significant reductions in diastolic blood pressure. It is recognized that with prazosin use, there are generally no adverse changes noted between pre- and post-treatment lipid levels. The results of this study demonstrated a 243.5 mg/dl total cholesterol level at baseline and 229.5 mg/dl maintenance levels following prazosin treatment. In contrast, the results following propranolol treatment showed a tendency to increase plasma levels of triglycerides and very low-density lipoprotein cholesterol, and to reduce levels of high-density lipoprotein cholesterol and high-density lipoprotein2 cholesterol. Because of a great deal of variability in lipid responsiveness to the study drug, none of the above changes attained statistical significance. Additional data from this ongoing study are required to confirm these preliminary observations.