We report the use of hyperbaric oxygen therapy (HBO2) in the treatment of an unusual case of secondary infertility. The patient had failed to conceive after a 1-year period of in-vitro fertilization, during which oral sildenafil had also been administered. However she became pregnant after an IVF cycle and the use of adjunctive HBO2 and sildenafil, which was administered intravaginally on this occasion. There is currently very little evidence to support the use of HBO2 in this context. The possible mechanisms of action of HBO2 in this case are discussed.