In view of the important impact of small-artery structural and functional abnormalities on complications of hypertension and recent data suggesting that some antihypertensive agents may correct some of these abnormalities, a study of resistance artery structure and function in 20 well-controlled essential hypertensive patients who had received for a prolonged period of time monotherapy with the once-a-day extended release formulation of the calcium channel antagonist nifedipine (nidefipine GITS) or with the beta-blocker atenolol is reviewed. Resistance-size small arteries (standardized lumen diameter of 247 +/- 8 microns) were studied after dissection from a gluteal subcutaneous biopsy. Small arteries were investigated on a wire myograph and as pressurized vessels. On the myograph, the media width-to-lumen diameter ratio of arteries was 5.37 +/- 0.09% in normotensive subjects, 5.38 +/- 0.18% in patients treated with nifedipine GITS, 6.81 +/- 0.18% in patients treated with atenolol and 7.08 +/- 0.12% in untreated hypertensives (p < 0.001, untreated or atenolol-treated patients vs. normotensives or nifedipine-GITS-treated hypertensives), and similar results were found in pressurized arteries. Contractility and endothelium-dependent relaxation were impaired in small arteries from untreated or atenolol-treated patients in comparison to those from normotensive subjects or nifedipine-GITS-treated patients. In conclusion, hypertensive patients with well-controlled blood pressure under treatment for more than 1 year with nifedipine GITS exhibit normal structure and function of small arteries, whereas similar patients whose blood pressure is as well controlled by the beta-blocker atenolol present abnormally thick small arteries with impaired contractility and endothelium-dependent relaxation. It will be important to determine whether small arteries of other vascular beds are also improved by nifedipine GITS treatment of elevated blood pressure and whether this results in reduced morbidity and mortality in hypertensive patients.