An epidemic of infections after video-assisted surgery (1,051 possible cases) caused by rapidly growing mycobacteria (RGM) and involving 63 hospitals in the state of Rio de Janeiro, Brazil, occurred between August 2006 and July 2007. One hundred ninety-seven cases were confirmed by positive acid-fast staining and/or culture techniques. Thirty-eight hospitals had cases confirmed by mycobacterial culture, with a total of 148 available isolates recovered from 146 patients. Most (n ؍ 144; 97.2%) isolates presented a PRA-hsp65 restriction pattern suggestive of Mycobacterium bolletii or Mycobacterium massiliense. Seventy-four of these isolates were further identified by hsp65 or rpoB partial sequencing, confirming the species identification as M. massiliense. Epidemic isolates showed susceptibility to amikacin (MIC at which 90% of the tested isolates are inhibited [MIC 90 ], 8 g/ml) and clarithromycin (MIC 90 , 0.25 g/ml) but resistance to ciprofloxacin (MIC 90 , >32 g/ml), cefoxitin (MIC 90 , 128 g/ml), and doxycycline (MIC 90 , >64 g/ml). Representative epidemic M. massiliense isolates that were randomly selected, including at least one isolate from each hospital where confirmed cases were detected, belonged to a single clone, as indicated by the analysis of pulsed-field gel electrophoresis (PFGE) patterns. They also had the same PFGE pattern as that previously observed in two outbreaks that occurred in other Brazilian cities; we designated this clone BRA100. All five BRA100 M. massiliense isolates tested presented consistent tolerance to 2% glutaraldehyde. This is the largest epidemic of postsurgical infections caused by RGM reported in the literature to date in Brazil.Outbreaks, pseudooutbreaks, and cases of health-care-associated infections caused by rapidly growing mycobacteria (RGM) have been reported since the first case was described in 1938 (13). In virtually all nosocomial infections caused by this group of microorganisms, there were failings in the sterilization processes of solutions, surgical instruments, or medical devices (13,14,45). Recent publications indicate an increasing number of infections secondary to breast augmentation and video-assisted surgeries (7,9,19,23,25,(40)(41)(42)(43).The growing number of cases and reports may be due, at least in part, to the well-known tolerance to alkaline glutaraldehyde among Mycobacterium chelonae-Mycobacterium abscessus group isolates and to the low susceptibility to high-level disinfectants (20,22,39).Outbreaks of RGM infections unrelated to medical procedures also can occur and usually are associated with exposure to recreational water containing a large number of bacteria and inadequate chlorination (15,44), highlighting the ubiquity of these organisms in the environment. In fact, RGM have been recovered from many different environmental sources, including soil and water distribution systems (8,45). RGM are considered opportunistic pathogens and can cause chronic lung disease, particularly the species included in the M. chelonae-M. abscessus group (8, 46)...