The findings of this study show that the diseases of the diabetic pilots were not under control at the time of their accidents. In addition, there were a significant number of pilots with elevated glucose and blood hemoglobin A1c (HbA1c) concentrations, suggesting undiagnosed and unreported diabetic conditions. Concentrations of glucose greater than 125 mg/dL in vitreous fluid and greater than 100 mg/dL in urine are considered to be elevated glucose levels indicative of hyperglycemia. Out of the 1,335 pilot deaths during the period reviewed, data were available from 363 vitreous fluid, 365 urine, and 607 vitreous fluid and urine analyses. These analyses showed that 43 pilots had elevated glucose in vitreous fluid and/or in urine. Of the 20 pilots whose blood samples were analyzed, 9 had HbA1c greater than 6 percent. Four were known diabetics, and five were unknown diabetics. Thirty of the 43 pilots had elevated glucose and HbA1c, suggesting undiagnosed/unreported diabetic conditions. These findings indicate the need for greater attention to controlling diabetes in pilots in coordination with Aviation Medical Examiners. 4 tables, 1 figure, and 24 references