Acute disc swelling was documented in 21 eyes of 12 patients with long-standing juvenile diabetes. All but one patient were in the second or third decade of life, with a 13-year average duration of diabetes. Seventeen eyes had initial acuity of 20/50 or better, including nine eyes with 20/25 or better; disc swelling was asymptomatic in six eyes. Simultaneous bilateral disc swelling occurred in seven patients. With no specific therapy, vision generally recovered to normal levels within a few weeks, but a few patients retained arcuate, nerve fiber bundle, field defects and optic atrophy. There was no positive correlation with the degree of diabetic retinopathy, and disc swelling did not seem to be a harbinger of progressive retinopathy or proliferation at the nerve head. Disc swelling in juvenile diabetics represents a distinct clinical entity that must be distinguished from other causes of acquired nerve head elevation, especially papilledema of increased intracranial pressure.