Louisiana is known to be an area endemic for Mycobacterium kansasii (MK). Since MK tends to disseminate in immunocompromised patients, one might, therefore, expect to observe an increasing number of MK infections associated with human immunodeficiency virus (HIV-1). A systematic 60-month review of clinical, microbiologie, and radiographie data associated with MK was performed from two major referral centers in New Orleans. From June 30, 1983 through June 30, 1988, MK was isolated from 72 patients. Twenty-three of the 72 (31.9%) were found to be coinfected with HIV-1. Over the 5-year study period, the phenomenon of dual infection increased from 0 to 50%. Six cases of extrapulmonary infection were found among the HIV-1 patients as compared to 1 in 49 non-HIV patients (p= 0.003, Fisher's exact test). In addition, patients with dual infection had atypical chest radiographs, usually with interstitial infiltrates without cavitation. Most of these patients died within 12 months (90.9%). When treatment was administered at all, often it varied considerably from patient to patient despite the well-known in vitro efficacy of certain widely available anti-mycobacterial agents.