To determine the population-based incidence of lower-extremity cellulitis. We performed a population-based survey with the resources of the Rochester Epidemiology Project in Olmsted County, Minnesota. We identified residents of Olmsted County who sought care for cellulitis from January 1, 1999, through December 31, 1999, reviewed medical records to ascertain agreement with a case definition of lower-extremity cellulitis, and calculated the population-based incidence of lower-extremity cellulitis. During 1999, 176 episodes met the case definition of lower-extremity cellulitis; the incidence of lower-extremity cellulitis in Olmsted County was 199 per 100,000 person-years. Sex-specific incidence was 197 per 100,000 person-years for women and 201 per 100,000 person-years for men. In a sex-adjusted model, the incidence increased 3.7% (95% confidence interval, 2.9%-4.5%) per year increment in age or 43.8% (95% confidence interval, 33.6%-54.7%) per 10-year increment. The incidence of cellulitis significantly increased with age (P<.001 in Poisson regression) but was not statistically significantly different between the sexes. The incidence of lower-extremity cellulitis in this population-based study was high and was affected by age. In contrast, sex did not influence infection incidence. The need for hospitalization and the prevalence of recurrence of lower-extremity cellulitis added to the burden of disease in Olmsted County.