This proposal in a pilot study of the feasibility of recruitment, ran- domization and follow-up of hypertensive black patients with reduced renal function. Phase I is a 12-month period (Jul 92 - Jun 93) for development of a protocol and manual of operations during monthly meetings of four clinical centers, the data coordinating center and NIDDK project coordinator(s). Phase II (Jul 93 - Jun 94), is recruitment of a sample of at least 25 black patients with documented diastolic HBP and reduced renal function. These 25 patients will be randomized to one of four treatment arms: stan- dard therapy versus therapy with angiotensin converting enzyme inhibitors and/or calcium channel blockers, and assignment within each treatment group to two levels of diastolic BP control: usual (MAP less than 107 mm Hg) and aggressive (HAP less than 92 mm Hg). BP and renal function (125-I iothalamate GFR measurements) will be assessed serially during a 12-month follow-up period. Phase III (Jul 94 - Mar 95) is a 9-month close-out period for data analysis. To accomplish the objectives of the RFA, we offer a collaborative pro- posal from Emory University and Morehouse School of Medicine. This will provide access to a large number of inner-city black hypertensive patients with reduced renal function, a team highly experienced in recruitment of minority participants into clinical trials, a General Clinical Research Center with staff trained in infusion techniques and precise timing of blood and urine specimens, and investigators with expertise in research on variables that influence progression of renal disease in hypertensive patients. The results will improve the understanding of the excess of hyperten- sion-related end-stage renal disease in blacks, and provide guidelines for a full-scale cooperative clinical trial.