We determined the effects of 6 years of lifestyle intervention in persons with impaired glucose tolerance (IGT) on the development of retinopathy, nephropathy and neuropathy over a 20 year period. In 1986, 577 adults with IGT from 33 clinics in Da Qing, China were randomly assigned by clinic to a control group or one of three lifestyle intervention groups (diet, exercise, and diet plus exercise). Active intervention was carried out from 1986 to 1992. In 2006 we conducted a 20 year follow-up study of the original participants to compare the incidence of microvascular complications in the combined intervention group vs the control group. Follow-up information was obtained on 542 (94%) of the 577 original participants. The cumulative incidence of severe retinopathy was 9.2% in the combined intervention group and 16.2% in the control group (p = 0.03, log-rank test). After adjusting for clinic and age, the incidence of severe retinopathy was 47% lower in the intervention group than the control group (hazard rate ratio 0.53, 95% CI 0.29-0.99, p = 0.048). No significant differences were found in the incidence of severe nephropathy (hazard rate ratio 1.05, 95% CI 0.16-7.05, intervention vs control, p = 0.96) or in the prevalence of neuropathy (8.6% vs 9.1%, p = 0.89) among the 20 year survivors. Lifestyle intervention for 6 years in IGT was associated with a 47% reduction in the incidence of severe, vision-threatening retinopathy over a 20 year interval, primarily due to the reduced incidence of diabetes in the intervention group. However, similar benefits were not seen for nephropathy or neuropathy.