Records of 5832 animals from The Upjohn Company Chinese Hamster colony, for the period December 1966 to September 1969, have been collected and stored on a magnetic tape file. These data have been analyzed for onset of diabetes and longevity. — The time at which 50% of the animals became diabetic (OT50) was 8.3 months during 1966; 4.3 months during 1967; 2.6 months during 1968; and 2.2 months during the first eight months of 1969. As time passed, the onset of diabetes became more uniform and predictable. Early in the colony history, onset of diabetes was quite variable, occurring from 2 to 31 months of age. Nondiabetics were not identified as such unless they were glucosuria-free for the first 15 months of age. It now appears that most animals which will become diabetic develop glucosuria by 5 months of age. This may permit earlier selection of nondiabetic control animals. Therefore, it may be possible to evaluate a variety of treatments on both onset of diabetes and longevity of the diabetic. — The longevity data show that, for the thirty-three month period of time studied, 50% of the total diabetic population were dead by 14.4 months of age. In contrast, 15 months of nonglucosuria was required to define an animal as nondiabetie. No significant difference was seen in the longevity of diabetics and nondiabetics surviving 15 months or longer.