We analyzed entry data from 163 adult hemoglobin SS and Sbeta(0) thalassemia patients enrolled in the prospective Sickle Cell Pulmonary Hypertension Screening Study and stratified their ECHO-determined tricuspid regurgitant jet velocity (TRV) and serum creatinine concentration according to three systemic blood pressure categories. TRV was >or= 2.5 m/sec in 27% of the patients with systolic blood pressure (SBP) <120 mmHg and diastolic blood pressure (DBP) <70 mmHg, in 37% with SBP 120-139 mmHg or DBP 70-89 mmHg, and in 93% with SBP 140 mmHg or DBP 90 mmHg or higher (P<0.0005 for trend). Serum creatinine concentration was 1.0 mg/dL or higher in 7% of patients with SBP <120 mmHg and DBP <70 mmHg, in 17% with SBP 120-139 mmHg or DBP 70-89 mmHg and 50% with SBP 140 mmHg or DBP 90 mmHg or higher (P<0.0005 for trend). Over 2 years of follow-up, there were trends for more frequent progression to elevated TRV (P=0.073) or creatinine (P=0.037) values according to the higher systemic blood pressure categories. Our findings suggest that systemic SBP 120-139 mmHg or DBP 70-89 mmHg defines a category of relative systemic hypertension in patients with sickle cell disease that is associated with increased risk for pulmonary hypertension and renal dysfunction. Whether antihypertensive and/or nitric oxide donor therapy in sickle cell disease patients with relative hypertension prevents these and other complications should be determined by clinical trials.