There are no population-based incidence studies of hidradenitis suppurativa (HS). Using the medical record linkage system of the Rochester Epidemiology Project, we sought to determine the incidence of the disease, as well as other associations and characteristics, among HS patients diagnosed in Olmsted County, Minnesota, between 1968 and 2008. Incidence was estimated using the decennial census data for the county. Logistic regression models were fit to evaluate associations between patient characteristics and disease severity. A total of 268 incident cases were identified, with an overall annual age- and sex-adjusted incidence of 6.0 per 100,000. Age-adjusted incidence was significantly higher in women compared with men (8.2 (95% confidence interval (CI), 7.0-9.3) vs. 3.8 (95% CI, 3.0-4.7). The highest incidence was among young women aged 20-29 years (18.4 per 100,000). The incidence has risen over the past four decades, particularly among women. Women were more likely to have axillary and upper anterior torso involvement, whereas men were more likely to have perineal or perianal disease. In addition, 54.9% (140/255) patients were obese; 70.2% were current or former smokers; 42.9% carried a diagnosis of depression; 36.2% carried a diagnosis of acne; and 6% had pilonidal disease. Smoking and gender were significantly associated with more severe disease.