Numerous in vitro investigations have reported that prolonged, continuous hyperbaric oxygen (OHP) exposure to certain bacteria and yeast is bacteriostatic. While it is tempting to attribute the lower infection rates reported in OHP-treated patients to this bacteriostatic effect, the duration and intensity of OHP exposure in these experimental studies exceeds that of normal therapeutic use. This study was designed to investigate the effects of human OHP treatment protocols upon the in vitro growth and survival of Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans. Additional studies using antibiotic-containing culture media were conducted to investigate the possible OHP enhancement of antibiotic sensitivity. No differences were observed between the bacterial and yeast growth curves of the control and experimental group. OHP also failed to produce any measurable difference in the bactericidal effectiveness of the selected antibiotics.