A 48-year-old male developed fever and sore throat while in Spain and was admitted to hospital, dehydrated, ketotic, pyrexial, and with a blood glucose of 35 mmol/l. Despite treatment with intravenous fluids, insulin, cephalosporin, potassium and bicarbonate he returned to Britain 7 days later, underhydrated and acidotic, though euglycaemic. His face was discoloured, there was painless nasal and maxillary swelling, oral candidiasis, and he went on to develop ophthalmoplegia and sudden blindness. Staphylococcus albus and mycelial fungus were isolated, the latter was identified as Mucor hiemalis, but despite treatment with amphotericin B co-ordinated with radical maxillary-facial surgery he died 31 days after the initial symptoms. Rhinocerebral mucormycosis is a recognized complication of ketoacidosis which is rarely reported in the UK. The organism invades arteries aggressively, therefore radical therapy must be started early to prevent the high mortality.