A rapidly growing mycobacterium was isolated in pure culture from the sputum of a 78-year-old woman suffering from hemoptoic pneumonia. The isolate exhibited an antimicrobial susceptibility pattern and a biochemical profile similar to that of Mycobacterium septicum ATCC 700731(T) and shared 100% 16S rRNA gene sequence similarity with this type strain over 1480 bp. Its partial rpoB sequence shared 98.2% similarity with the latter species, suggesting the isolate was representative of a sequevar of M. septicum. Contrary to the type strain, this isolate was resistant to azithromycin, erythromycin, vancomycin and tobramycin. This case illustrates the first isolation from sputum of M. septicum, a member of the Mycobacterium fortuitum group previously isolated once from bacteremia. Strain D13 has been deposited in the Collection de l'Institut Pasteur as CIP 108512.