Rapid detection of drug resistance in Mycobacterium tuberculosis is essential for efficient treatment and control of this pathogen. The amplification refractory mutation system (ARMS) was used to detect mutations in the rifampin resistance-determining region of the rpoB gene. A total of 39 rifampin-resistant M. tuberculosis isolates in Shanghai were analyzed by this assay, resulting in 92.3% sensitivity (36 of 39) and 87.2% concordance (34 of 39) relative to DNA sequencing, by which 41 mutations of 11 different types, including 9 point mutations and 2 deletions, were identified in the rpoB gene. The most frequent mutations were those associated with codon 531 (21 of 39 [53.8%]) and codon 526 (9 of 39 [23.1%]). The results suggest that the ARMS assay is rapid and simple to implement and could be performed for detection of rifampin resistance in M. tuberculosis to complement conventional culture-based methods.