What role can private voluntary regulation play in improving labor standards and working conditions in global supply chain factories? How does this system relate to and interact with other systems of labor regulation and work organization? This paper seeks to address these questions through a structured comparison of two factories supplying Nike, the world’s largest athletic footwear and apparel company. These two factories have many similarities - both are in Mexico, both are in the apparel industry, both produce more or less the same products for Nike (and other brands) and both are subject to the same code of conduct. On the surface, both factories appear to have similar employment (i.e., recruitment, training, remuneration) practices and they receive comparable scores when audited by Nike’s compliance staff. However, underlying (and somewhat obscured by) these apparent similarities, significant differences in actual labor conditions exist between these two factories. What drives these differences in working conditions? What does this imply for traditional systems of monitoring and codes of conduct? Field research conducted at these two factories reveals that beneath the code of conduct and various monitoring efforts aimed at enforcing it, workplace conditions and labor standards are shaped by very different patterns of work organization and human resource management policies.