Using an historical cohort study design with a 12 year follow-up, we found that 77 Navajo adults with type II diabetes mellitus were hospitalized at a rate of 335 hospitalizations per 1000 patient years compared to a rate of 167 hospitalizations per 1000 patient years for 77 age, sex, and residence matched non-diabetic controls, yielding a risk ratio of 2.0. Using matched pairs analysis (sign test), the observed difference in number of hospital admissions is statistically significant (z = 2.30, p less than 0.05). The average duration of hospitalization, however, was not statistically different in matched pairs analysis (z = 0.95, p greater than 0.05). The 136 excess hospitalizations of the diabetic subjects included 45 admissions for poor metabolic control of diabetes, 50 excess admissions for infectious disease, and 26 excess admissions for conditions of the heart, eye, kidney, or non-traumatic amputation. In multivariate analyses, variables found to be associated with greater hospitalization experience among the 77 diabetic subjects in the 12 years follow-up period included older age at entry to the study, poorer metabolic control early in the study period, and presence of diabetic complications.