The antihypertensive effects and tolerability of a once-daily, fixed combination of atenolol 50 mg and nifedipine retard 20 mg ('Nif-Ten') were monitored in a 12-month open study in 30 elderly hypertensive patients, whose blood pressure was inadequately controlled after four weeks treatment with atenolol 50 mg once daily. Sitting (and standing) blood pressure and heart rate one to four hours after dosing were recorded at entry (191/95 mmHg) and at the end of the run-in period (186/93 mmHg). After one month's therapy with the fixed combination the mean sitting blood pressure fell to 169/89 mm Hg and was maintained at this level for the entire 12-month period of observation. During the study four patients complained of side effects on fixed combination therapy with one patient withdrawn due to flushes and hot sweats. One other patient suffered flushes and hot sweats and two patients complained of mild dizziness. There were no demonstrable effects of fixed combination therapy upon the biochemical parameters measured. We conclude that the fixed combination of atenolol plus nifedipine retard was well tolerated over a 12-month period in the group of elderly hypertensive patients studied. The combination appears to exert a greater antihypertensive effect than the beta-blocker monotherapy with no evidence of tachyphylaxis, although these findings require confirmation in a controlled trial.