In some industrialized countries reemergence of tuberculosis has been recorded. Most cases are thought to be caused by reactivation of infections that had been acquired many years before, but in some geographical areas up to 40% of diagnosed infections have been estimated to be newly acquired, based on the results of molecular epidemiological methods. Restriction fragment length polymorphism of the insertion sequence IS6110 of Mycobacterium tuberculosis has been widely used to evaluate epidemiological patterns of transmission in various communities. We have used IS6110 fingerprinting to analyze 101 strains which were isolated between June 1994 and June 1998 from 95 inhabitants of the province of Palermo, Italy, an area with an endemic rate for tuberculosis ranging between 5.1 and 8.0 per 100,000 persons in the last 5 years. 89 different patterns have been obtained, 87.4% of the patients were infected by presumably unrelated isolates. Six microepidemics were also recognized. These data suggest that reactivation largely exceeds recent infection.