Abstract: Mycobacterium avium represents a health concern for both humans and pigs. The characterisation of its subspecies is an important step improving the understanding of the epidemiology and the control of this pathogen. Ninety-two human M. avium strains were selected fora retrospective study. Subspecies determination by rpoD sequencing and 151245/15901 analysis showed that 98.9% of Belgian human M. 01/10177 strains belong to the subspecies hominissuis (MAH). Some of these MAH strains present particular 151245/15901 profiles (absence of 151245 and false 15901 detection provoked by the presence of ISMov6). In addition, 54 MAH strains isolated from submandibular lymph nodes of Belgian pigs with lymphadenitis were included in this study. Genotyping of human and porcine isolates was performed using multispacer sequence typing (MST). In total, 49 different MST types were identified among pig (n= n) and human (n similar to 4]) MA isolates, with only five shared by both hosts. Among these MST types, 34 were newly identified. Our findings demonstrate the extensive genetic diversity among MAH isolates. Some genotypes were more prevalent in human or pigs but no correlation was observed between MST type and place of residence or the farm of origin for human and porcine isolates respectively, suggesting an environmental source of infection.