Rapidly growing mycobacteria, generally of low virulence, are capable of causing a wide spectrum of infections. Increasing reports in the literature, referral center experiences, and data from the Infectious Disease Society of America Emerging Infectious Disease Network suggest that greater numbers of infections are occurring. Epidemiological study is imperative in understanding the true incidence of these infections and preventing disease in vulnerable hosts. Especially problematic is pulmonary infection due to Mycobacterium abscessus, which is difficult to cure. New agents with enhanced activity against this group and other nontuberculous mycobacteria are needed. Here, we focus on the members of the rapidly growing mycobacteria because of their emerging importance in both sporadic infections and outbreak settings.