EBMtrialcentral- Comparing Initial Diuretic Therapies Using a Collaborative Network

* Clinical equipoise exists with respect to the important question, "What is the best initial diuretic for the treatment of Hypertension"? A pragmatic comparative effectiveness research (CER) study comparing Chlorthalidone to Hydrochlorthiazide (HCTZ) could help inform decision making for this common problem. * The investigators aim to harness both the power of bioinformatics (using web-based data-capture and electronic health records) and of online media (through collaboration) in order to facilitate such a CER in "usual-care" settings. This process may also provide a foundation for testing a wealth of important clinical questions which commonly arise in the delivery of contemporary healthcare and would otherwise be left unanswered. * To this end the investigators are developing a website, EBMtrialcentral, where eligible physicians can go online and join their collaborative network. Physicians can then enroll eligible patients in this study. These will include under-served urban patients. Clinical information will be entered online (using a secure database housed at Johns Hopkins), patient consent will be obtained electronically and treatment recommendations will be randomly allocated to either 25mg daily of oral HCTZ or 12.5mg daily of oral Chlorthalidone. The investigators aim to increase to 50mg HCTZ and 25mg Chlorthalidone over 8 weeks and compare their effects on BP measured with a 24 hour monitor. * The investigators' primary hypothesis is that non-blinded, random, parallel allocation of 12.5mg daily Chlorthalidone (titrated to 25mg at 4 weeks) will demonstrate a clinically meaningful ≥5mmHg improvement in BP control (as measured by change in BP from baseline using 24hr ABPM) compared to 25mg daily HCTZ (titrated to 50mg at 4 weeks) in newly hypertensive patients followed in a usual-care clinic setting over 8 weeks. They will also analyze differences in side-effects or safety (serum electrolytes) between these two medications.