An inexpensive method for determining significant sleep-related hypoxemia would be beneficial for patients being investigated and treated for sleep-disordered breathing in order to distinguish hypoxic patients from those without nocturnal hypoxemia. Since 2,3 diphosphoglycerate (DPG) which profoundly affects dissociation of O2 from hemoglobin is an instrumental subtance in determining the O2 affinity of blood, it becomes important to consider in what extent the nocturnal intermittent hypoxemia may change the levels of 2,3 DPG. In this study, we tested the hypothesis that 2,3 DPG levels of hypoxic SDB patients may be higher than that of nonhypoxic SDB patients and normal controls. Fourteen SDB patients were participated the study, seven with hypoxia (hypoxic group) who spent more than 10 minutes during sleep with SaO2<90% (mean 71 minutes), and seven SDB patients (nonhypoxic group) who spent less than 10 minutes during sleep with SaO2<90% (mean 6 minutes). Seven healthy non-smoking subjects were included as a control group. After giving informed consent, all participants underwent a venous blood sampling performed between 07:00 and 08:00 a.m. Blood 2,3 DPG levels were measured by using spectrophotometry. 2,3 DPG levels were 1.84±0.44, 1.68±0.18 and 1.71±0.11 mmol/mL in hypoxic, nonhypoxic and control groups respectively (p>0.05). In conclusion, to our knowledge this is the first study that has evaluated 2,3 DPG levels in hypoxic and non hypoxic types of SDB patients. Chronic intermittent hypoxia which is entirely a different entity from sustained hypoxia did not lead to increases in 2,3 DPG levels in both hypoxic and nonhypoxic SDB patients.