Zygomycosis is a rare but emerging mycosis. Because of the sub-optimal efficacy of the standard antifungal treatment for this disease, hyperbaric oxygen (HBO) has been used occasionally as an adjunctive therapeutic modality. A review of 28 published cases of zygomycosis indicates that adjunctive HBO may be beneficial in diabetic patients (94% survival), whereas its benefit in the small group of patients with haematological malignancies or bone marrow transplants is doubtful (33% survival; p 0.02). Prolonged courses of HBO were associated with a higher survival (100% survival; p 0.003). Additional studies are required to assess the optimal timing and dose for HBO treatment.