Soft-tissue infections caused by rapidly growing mycobacteria may follow penetrating trauma. We present four immunologically normal patients in whom soft-tissue infections with Mycobacterium fortuitum developed after they stepped on nails. Their presentations were clinically indistinguishable from puncture wound infections caused by Pseudomonas aeruginosa and Staphylococcus aureus. The acid-fast organisms grew on standard bacteriologic media within three to five days. Speciation and antimicrobial susceptibility testing was performed. The primary mode of therapy was surgical; adjunctive antimicrobial therapy is recommended only for extensive or chronic infections and in immunocompromised hosts. All four of our patients had good outcomes after therapy.