Patients with acquired immunodeficiency syndrome (AIDS) are at risk from many endocrine complications. Pentamidine has been recognised for its potential to cause symptomatic, and even life-threatening hypoglycaemia. We report two cases of diabetes mellitus presenting with ketoacidosis 3 to 4 months after pentamidine therapy for Pneumocystis carinii pneumonia (PCP), and review our experience of dysglycaemia in 58 patients with AIDS treated with pentamidine. These cases emphasise the potential for severe pancreatic toxicity in patients with AIDS. Hyperglycaemia during pentamidine therapy may be a marker for patients at increased risk of developing diabetes mellitus.