Objective: To estimate the progression rates to impaired glucose regulation (impaired fasting glucose or impaired glucose tolerance) and diabetes in the Danish population-based Inter99 study and in a high-risk subpopulation, separately. Research Design and Methods: From a population-based primary prevention study, the Inter99 study, 4,615 individuals without diabetes at baseline and with relevant follow-up data were divided into a low- and a high-risk group based on a risk estimate of ischemic heart disease or the presence of risk factors (smoking, hypertension, hypercholesterolemia, obesity, or having impaired glucose tolerance). High-risk individuals (57.1%) were examined with an oral glucose tolerance test at 1- and 3-year, and all the participants were re-examined at 5-year follow-up. Person-years at risk were calculated. Progression rates to impaired glucose regulation and diabetes were estimated directly from baseline to 5-year follow-up for all the participants, and from baseline through 1- and 3-, to 5-year follow-up for the high-risk individuals, separately. Results: In the combined low- and high-risk group, 2.1 per 100 person-years progressed from normal glucose tolerance to impaired glucose regulation or diabetes. Among high-risk individuals, 5.8 per 100 person-years with normal glucose tolerance progressed to impaired glucose regulation or diabetes, and 4.9 per 100 person-years progressed from impaired glucose regulation to diabetes. Conclusions: Progression rates to impaired glucose regulation using the current World Health Organization classification criteria were calculated for the first time in a large European population-based study. The progression rates to diabetes show the same pattern as seen in the few similar European studies.