To validate the specificity of the hsp65 PNA RT-PCR method in detecting M. abscessus group infections from sputum samples, we applied the technique to 30 sputum samples from different patients previously identified as infected with mycobacteria other than the M. abscessus group (10 patients with M. tuberculosis, 9 with M. avium, 7 with M. intracellulare, 1 with M. celatum, 1 with M. fortuitum, 1 with M. kansasii and 1 with M. szulgai) via rpoB PCR restriction analysis of the same cultures. The gene discussed is HSPD1; the disease is infection.