Antigen fingerprinting based on surface glycolipid antigens was applied to the epidemiology of clinical isolates of the Mycobacterium avium complex from 128 acquired immunodeficiency syndrome (AIDS) and 31 non-AIDS patients from several different regions of Spain. The application of thin-layer chromatography, gas chromatography-mass spectrometry and monoclonal antibodies, combined with ELISA, allowed a facile identification, differentiation and classification of the isolates. The cumulative results demonstrate that, among the clinical isolates, serovar 4 was predominant in both AIDS (33.6%) and non-AIDS (22.6%) isolates. In general, the results demonstrate geographical as well as disease-related differences in the distribution of Myco. avium complex serovars of clinical importance.