Sickle cell disease is characterized by microvascular occlusion and hemolytic anemia, factors that impair tissue oxygen delivery. We use visible reflectance, hyperspectral imaging to quantitate skin tissue hemoglobin oxygen saturation (HbO₂) and to determine whether changes in blood flow during nitric oxide (NO) stimulation or gas administration (therapies proposed for this disease) improve skin tissue oxygen saturation in 5 patients with sickle cell disease. Compared with 6 healthy African-American subjects, sickle cell patients exhibited higher forearm blood flows (7.4±1.8 versus 3.2±0.4 ml/min per 100ml tissue, P=0.037) but significantly reduced percentages of skin HbO₂ (61.0±0.2 versus 77.5±0.2, P<0.001). Administration of acetylcholine to patients increased blood flow by 15.1±3.8ml/min per 100ml of tissue and the percentage of skin HbO₂ by 4.1±0.3 (P=0.02, P<0.001, respectively, from baseline values). Sodium nitroprusside, a direct NO donor, increased blood flow by 3.9±1.1ml/min and the percentage of skin HbO₂ by 2.9±0.3 (P=0.02, P<0.001, respectively). NO inhalation had no effect on forearm blood flow, yet increased the percentage of skin HbO₂ by 2.3±0.3 (P<0.001). Percentages of skin HbO₂ were exponentially related to blood flow (R=0.99, P<0.001), indicating a limit to skin tissue oxygen saturation at high blood flows. Thus, for acetylcholine infusion leading to blood flows seven-fold greater than healthy resting African-American subjects, patients still exhibited lower percentages of skin HbO₂ (65.2±0.2 versus 77.5±0.2, P<0.001). Visible reflectance hyperspectral imaging demonstrates that either the stimulation or the administration of NO pharmacologically or by gas inhalation-improves, but does not normalize, skin tissue oxygen saturation in patients with sickle cell disease.