An evaluation of the microbiota present in cutaneous ulcers from 31 patients with a clinical and parasitological diagnosis of American tegumentary leishmaniasis (ATL) was carried out by the standard filter paper disc technique, including antimicrobial susceptibility of the bacterial isolates. Microbial examination indicated that 21 patients (67.7%) were contaminated with one to four bacteria and some of them also with yeast. A total of 142 micro-organisms were isolated. Staphylococcus aureus was the most frequently recovered bacterium (95.2% of positive patients) and was found to produce type B (70% of the staphylococcal isolates) and type C (50%) enterotoxins as well as toxic shock syndrome toxin (60%). Proteus mirabilis (33.3% of the positive patients), Streptococcus pyogenes (19.0 %), H(2)S-negative Proteus species (19.0%), Klebsiella oxytoca (14.3%), Enterobacter species (9.5%), Peptostreptococcus species (9.5%), Pseudomonas species (4.8%), Prevotella bivia (4.8%), Escherichia coli (4.8%), Streptococcus agalactiae (4.8%), Bacteroides fragilis (4.8%), Candida albicans (9.5%) and Candida tropicalis (4.8%) were also isolated. Surprisingly, Staph. aureus isolates were susceptible to almost all tested drugs, although some of them were resistant to penicillin (69%) and ampicillin + sulbactam (68%). Concerning obligate anaerobes, all the Gram-negative isolates (25% of the total) were resistant to metronidazole. The results of the present study show that microbial secondary contaminants, particularly Staph. aureus, should be considered in the diagnosis and treatment of ATL lesions.