OBJECTIVE: To evaluate the new non-radioactive automated method BACTEC 9000 MB system for the rapid detection of mycobacteria in clinical specimens. METHODS: Ninety clinical specimens from 90 patients with a clinical diagnosis of tuberculosis were tested by both BACTEC 9000 and standard microbiological methods, and the results compared. RESULTS: The BACTEC 9000, in comparison with the standard method, showed significantly higher detection rates (45 of 90 positive versus 34), shorter time to culture positivity (mean time 18.8 versus 27.4 days) and lower contamination rate (2.2% versus 5.5%). CONCLUSIONS: These results encourage the use of this new system and suggest its use in microbiological laboratories involved in mycobacteriology.