- Previous work has established a surprisingly high prevalence of acanthosis nigricans (AN) and its association with increased risk of type 2 diabetes in a Southwestern practice-based research network (PBRN). Our objective was to establish whether this high prevalence of AN would be present in other areas.We examined the prevalence of type 2 diabetes and its risk factors and the prevalence of AN among patients aged 7 to 65 years who had been seen by one of 86 participating clinicians in a national PBRN consortium during a 1-week data collection period. In a subsample of nondiabetic matched pairs who had or did not have AN, we compared fasting glucose, insulin, and lipid levels.AN was present in 19.4% of 1730 patients from among all age ranges studied. AN was most prevalent among persons with more risk factors for diabetes. Patients with AN were twice as likely as those without AN to have type 2 diabetes (35.4% vs 17.6%; P < .001). In multivariable analysis, the prevalence ratio for diabetes was 2.1 (95% CI, 1.3-3.5) among non-Hispanic whites with AN and 1.4 (95% CI, 1.1-1.7) among minority patients with AN. In a subsample of 11 matched pairs, those with AN had higher levels of insulin and insulin resistance.We found high rates of AN among patients in primary care practices across the country. Patients with AN likely have multiple diabetes risk factors and are more likely to have diabetes.