Patients with chronic obstructive pulmonary disease (COPD) may benefit from ambulatory oxygen; however, the effect of exercise on arterial oxygen saturation (Sa,O2) in patients with kyphoscoliosis and of correction with ambulatory oxygen have not been previously reported. Twelve patients with stable kyphoscoliosis (mean (SD) Cobb angle 79 (26) degrees) were studied, with mean (SD) arterial oxygen tension (Pa,O2) 8.96 (0.93) kPa, arterial carbon dioxide tension (Pa,CO2) 6.52 (0.66), forced expiratory volume in one second (FEV1) 0.90 (0.15) L, forced vital capacity (FVC) 1.34 (0.46) L. Six-minute walking tests with oximetry and visual analogue scores (VAS) for breathlessness were performed on air (baseline), and with cylinders containing air and oxygen at 2 L-min-1. Cylinder walks were in random order, with patients blinded to cylinder content. Patients showed oxygen desaturation at each stage of the study. At baseline, oxygen desaturation during exercise was correlated with deterioration in VAS breathlessness scores. Ambulatory oxygen produced significant improvements in desaturation, breathlessness scores and recovery time compared to baseline and air cylinder walks. There was no relationship between baseline desaturation and changes in walking distance. Although exercise desaturation, breathlessness and recovery times were significantly improved with ambulatory oxygen at 2 L.min-1, walking distance was unaffected. We conclude that patients with moderate to severe kyphoscoliosis have significant oxygen desaturation on exercise and should thus routinely receive oximetry on exercise and assessment for ambulatory oxygen therapy.