A unique case of HAPE precipitating diabetic ketoacidosis in a previously undiagnosed Type 2 diabetic is reported. A 39-year-old male, previously well, was admitted at a hospital situated at a height of 3500 m with complaints of increasing breathlessness on effort, cough, and fever of short duration, 5 days after high altitude reascent. Examination at admission revealed a febrile (38 degrees C) patient with tachycardia (104/min), SaO2 was 82% (on supplemental oxygen), chest examination revealed bilateral crackles in all lung fields, and chest radiograph demonstrated bilateral fluffy heterogeneous opacities in all zones. He was diagnosed as suffering from high altitude pulmonary edema. The patient did not show adequate improvement despite conventional treatment for HAPE with supplemental oxygen and rest. Investigations revealed leucocytosis, and urinalysis revealed glycosuria and ketonuria. Subsequent arterial blood gas analysis revealed that acidemia and serum glucose levels were raised. He was thereafter managed as for HAPE and DKA and recovered in 2 weeks. The patient has been on regular follow-up with satisfactory glycemic control with oral hypoglycemic agents.