We applied four molecular techniques for the typing of strains of Mycobacterium tuberculosis associated with outbreaks: RFLP of the IS6110 insertion sequence, spoligotyping, RAPD, and PCR-IS6110. All 4 techniques were applied to 18 strains which were shown by epidemiological data to be involved in 6 outbreaks. All the methods classified the strains into the same groups as the classical epidemiological data did, but RFLP of the IS6110 insertion sequence and spoligotyping are laborious techniques requiring more than a full day's work, whilst RAPD and PCR IS6110 are simple methods easily incorporated into the daily routine. Nevertheless, a large-scale process of standardization and evaluation is necessary in order to be able to establish the true value of the latter two methods as intraspecific characterization markers for M. tuberculosis isolates.