1 Enalapril 20 mg, propranolol 160 mg, atenolol 50 mg and placebo each were given once a day for 8 days to 12 normal volunteers, using a Latin-square design and double-blind procedures. A battery of tests was applied before, 2 and 4 h after the dose on day 1 and 8. 2 EEG effects were detected on day 8 with propranolol but not consistently after atenolol or enalapril. 3 Reaction-time, symbol copying and memory were impaired with propranolol; only memory was marginally affected by atenolol. Enalapril impaired memory but improved tapping ability. 4 Subjectively, propranolol was associated with drowsiness, enalapril with calmness and perhaps contentedness. Ratings of headache were increased with enalapril. 5 It is concluded that the apparent beneficial subjective effects of enalapril in clinical practice are attributable partly to intrinsic central effects but mainly to the contrast with beta-adrenoceptor blockers such as propranolol.