Disorders of fatty acid oxidation and organic acid metabolism produce serious clinical problems including death. Introduction of MS/MS technology for newborn screening allowed detection of these disorders in a single process, more than doubling the number of disorders that can be detected from dried-blood spots in newborn screening. Expanded newborn screening has become a critical issue with increased public awareness and demands. Screening by MS/MS is operational in several private testing and public health laboratories. Guidelines and quality assurance services are essential to enhance program expansions. The first of two workshops was organized in June 2000 and the second in September of 2001 to discuss procedures for integrating MS/MS into newborn screening programs. Both workshops addressed technical problems encountered with implementing MS/MS testing. One outcome of the first workshop was a pilot survey for assessing performance of MS/MS laboratories worldwide, which occurred in September 2000. This pilot survey led to the expansion of the proficiency testing services to include MS/MS testing. There are 32 participating laboratories, three of the ten countries represented are from the Asia-Pacific Region.