We conducted a randomised double-blind crossover comparison of felodipine, 10 mg once daily, nifedipine 20 mg twice daily, each treatment being given as a monotherapy for four weeks. Active treatment was preceded by a two-week placebo run-in. Both systolic (SBP) and diastolic (DBP) blood pressures (supine and erect) fell significantly (all P less than 0.001) following both drug treatments. Nifedipine produced a greater orthostatic effect, and hence a significantly greater fall in erect SBP than felodipine (P less than 0.05). There was no significant difference between the effects of the drugs on DBP. Achieved DBP was 90 mmHg or less in 18/22 patients on felodipine and 18/22 patients on nifedipine. Both drugs were well-tolerated. Felodipine given once daily was effective as a monotherapy for the control of mild to moderate hypertension and compared favourably with twice daily nifedipine.