Nineteen isolates of Mycobacterium haemophilum were analyzed by pulsed-field gel electrophoresis of large restriction fragments generated by digestion of chromosomal DNA with XbaI. Six patterns were observed. Twelve of 16 M. haemophilum isolates (75%) collected in the New York Metropolitan Area from 1990 to 1991 shared the same pattern, including all six isolates submitted from one hospital. Two different patterns were seen among the other four isolates. Individual isolates from Albany, N.Y., Florida, and Texas had unique patterns. Pulsed-field gel electrophoresis is the first method reported with the capability to type strains of M. haemophilum and will hopefully provide insight into the source and transmission of this emerging pathogen.