OBJECTIVE To test reports that beta blockers, particularly lipophilic forms, impair cognitive function and cause psychiatric disturbances. METHODS Randomized, double-blind, controlled crossover trial with eight-week treatment periods. METHODS Sequential sample of 42 male veterans, with untreated diastolic blood pressures (DBP) between 90 and 110 mmHg, aged 35-64 years. METHODS Propranolol-LA, 80-mg tablets, or atenolol, 50-mg tablets, were given daily, incremented by one tablet at weekly intervals until DBP less than or equal to 90 mmHg. Hydrochlorothiazide was added, if necessary. RESULTS Repeated-measures ANOVA was performed on all cognitive tests. Cognitive test performance was not affected by beta blocker therapy in seven of nine tests and was enhanced on Trail Making Test. Performance was impaired only on Digit Cancellation. Neither Speilberger's State Trait Anxiety Inventory nor the Beck Depression Inventory was affected by either beta blocker. CONCLUSIONS Atenolol or propranolol therapy does not impair cognitive function or contribute significantly to psychiatric side effects.