This study was undertaken to clarify whether pulmonary hypertension is a useful marker for underlying obstructive sleep apnea in patients with edema. Twenty-eight ambulatory adults with bilateral leg edema and a normal echocardiogram were enrolled. Sixteen subjects had pulmonary hypertension, and 12 subjects had normal pulmonary artery pressures. Spirometry, pulse oximetry on room air, and polysomnography were obtained for each subject. Ten of 16 (63%) pulmonary hypertension subjects and 9 of 12 (75%) nonpulmonary hypertension subjects had obstructive sleep apnea (P =.48). Eleven of 16 (69%) pulmonary hypertension subjects and 11 of 12 (92%) nonpulmonary hypertension subjects were obese (P =.20). If these results are generalizable, obstructive sleep apnea is frequently associated with bilateral leg edema and obesity, regardless of the presence of pulmonary hypertension. Thus, especially in obese patients, bilateral leg edema may be a useful clinical marker for underlying obstructive sleep apnea.