Mycobacteria were isolated from 1,591 (78%) of 2,036 porcine tissues submitted to Veterinary Services Laboratories over a 3-year period (July 1, 1971, to June 30, 1974). The isolates were identified by biochemical and serologic tests. Of the 1,547 Mycobacterium avium isolates, 452 were serotype 1, 728 were serotype 2, 60 were serotyped 4, 110 were serotype 8, and 51 were serotyped 10; 36 isolates represented 11 other serotypes; 65 isolates shared antigens with more than one serotype; and 45 isolates, untypabley serologic methods, were identified by pathogenicity in chickens as M avium. Mycobacterium bovis was isolated from 15 tissues; Mycobacterium fortuitum, from 3; and Mycobacterium paratuberculosis, Mycobacterium scrofulaceum, and Mycobacterium xenopi were each isolated from single specimens.