Nontuberculous mycobacteria (NTM) infection is a frequent opportunistic infection in patients infected with the human immunodeficiency virus. However, NTM infection may also occur in nonimmunocompromised hosts. In order to determine the spectrum of mycobacterial infection in the nonacademic setting, we analyzed the demographic and clinical characteristics of all patients presenting to a suburban multispecialty clinic during a 24-mo period. Twenty-one patients presented with active mycobacterial lung infections during the study period. Of these, only one had Mycobacterium tuberculosis. The remaining 20 had lung infections with NTM. One patient was infected with M. kansasii, three had M. abscessus, and 16 had M. avium complex. One patient with disseminated M. avium infection met the diagnostic criteria for the acquired immunodeficiency syndrome. The remaining 19 were largely normal at presentation and were predominantly elderly (mean age, 71 +/- 11 yr), female (79%), nonsmokers (89%) who presented with cough (94%) and localized radiographic infiltrates (84%), often in the right middle lobe and/or lingula (73%). The predominance of nontuberculous mycobacteria over M. tuberculosis in our practice was mirrored by results of an 11-yr review of experience from a nearby suburban hospital, where 65% of mycobacterial infections in the previous 5 yr were with NTM. We conclude that infection with NTM represents a previously underappreciated cause of chronic lung infection among elderly middle-class patients in the community setting.