We describe a patient who presented with orbital apex syndrome. Sphenoidectomy and biopsy revealed invasive zygomycosis. The patient had no obvious risk factors for the development of zygomycosis, but was subsequently found to have a solitary, occult lung carcinoma. The unusual clinical features of this case are discussed, and the English language literature on zygomycoses in patients with solid tumours is reviewed. Possible predisposing factors are discussed.