Abstract： Objective To study the effects of HBO on CD34+ cells and white blood cells in peripheral blood in patients with spinal cord injuries.Methods Twenty-one cases of spinal cord injuries were randomly divided into 2 groups:the control group ( n =10) and the HBO group ( n =11 ).The control group received routine treatment ( including orthopaedic surgery,drug treatment,as well as acupuncture),while the HBO group received routine treatment and HBO therapy,with HBO exposure once a day for a succession of 20 days.Venous blood was collected on the 5th,10th and 20th days both before and after treatment for the detection of white blood cells (WBC) and the absolute CD34 + cells.Results HBO could elevate the absolute count of peripheral blood CD34 + cells(P ＜ 0.05 ),but no significant effect could be noticed on the count of white blood cells(P ＞0.05).The outline of the absolute counts of peripheral blood CD34+ cells for the HBO group and the control group indicated that they tended to change in a different way.The HBO group tended to increase more significantly,while no significant changes could be detected in the control group.Conclusions Successive exposures to HBO could mobilize stem cells derived from the bone morrow of the patients with spinal cord injuries to be released to the peripheral blood,thus,the absolute count of peripheral blood CD34 + cells was maintained at a relatively high level,while no obvious effect could be monitored on WBC count.