Abstract-We assessed adverse metabolic effects of atenolol and hydrochlorothiazide among hypertensive patients with and without abdominal obesity using data from a randomized, open-label study of hypertensive patients without evidence of cardiovascular disease or diabetes mellitus. Intervention included randomization to 25 mg of hydrochlorothiazide or 100 mg of atenolol monotherapy followed by their combination. Fasting glucose, insulin, triglycerides, high-density lipoprotein cholesterol, and uric acid levels were measured at baseline and after monotherapy and combination therapy. Outcomes included new occurrence of and predictors for new cases of glucose Ն100 mg/dL (impaired fasting glucose), triglyceride Ն150 mg/dL, high-density lipoprotein Յ40 mg/dL for men or Յ50 mg/dL for women, or new-onset diabetes mellitus according to the presence or absence of abdominal obesity. Abdominal obesity was present in 167 (58%) of 395 patients. Regardless of strategy, in those with abdominal obesity, 20% had impaired fasting glucose at baseline compared with 40% at the end of study (PϽ0.0001). Proportion with triglycerides Ն150 mg/dL increased from 33% at baseline to 46% at the end of study (PϽ0.01). New-onset diabetes mellitus occurred in 13 patients (6%) with and in 4 patients (2%) without abdominal obesity. Key Words: atenolol Ⅲ hydrochlorothiazide Ⅲ abdominal obesity Ⅲ metabolic syndrome Ⅲ new-onset diabetes mellitus Ⅲ hypertension I t is estimated that Ͼ72 million US adults are obese, affecting 33% of men and 35% of women. 1 This epidemic is associated with increased mortality, 2 primarily via metabolic and cardiovascular (CV) complications. Abdominal fat accumulation increases CV disease risk independent of overall adiposity. 3 The presence of abdominal obesity provides additional predictive information for the development of CV morbidity and mortality compared with increased body mass index alone. 4 Hypertension requiring treatment is highly prevalent in those with obesity and abdominal obesity, regardless of sex or ethnicity, and is poorly controlled. [5][6][7] Some antihypertensives are associated with adverse metabolic effects (AMEs), including hyperglycemia, hypertriglyceridemia, and hyperuricemia. 8 The predisposing factors for these AMEs are unknown, but preexisting abdominal obesity may contribute. Although there are many studies in older, high-risk populations indicating that thiazide diuretics and -blockers increase the incidence of new-onset diabetes mellitus compared with other antihypertensive regimens, 9 our knowledge is incomplete with regard to the development of