Mycobacterium szulgai is a newly recognised species of mycobacteria whose pathogenicity in man can only be confirmed following certain criteria. We report a new observation comprising three points of interest. M. szulgai appears to be directly responsible for pulmonary infection and the clinical and radiological progress is very rapid. The human disease probably comes from infected water in aquaria. We have reviewed other cases of M. szulgai in the literature and for two out of three amongst these there is pulmonary involvement resembling tuberculosis; in the other cases cutaneous disease, synovial disease and bone disease have been described.