With the potential for catching serious metabolic disorders before symptoms appear, medical laboratories in the United States are increasingly screening newborns using tandem mass spectrometry (MS/MS) technology. A recent Morbidity and Mortality Weekly Report by the Centers for Disease Control and Prevention (CDC) shows about 500,000 newborns underwent such screening last year, up from 60,000 in 1996. This report, "Using Tandem Mass Spectrometry for Metabolic Disease Screening Among Newborns" (www.cdc.gov/mmwr/preview/mmwrhtml/rr5003a1.htm), evaluates barriers and offers recommendations and standards for states interested in implementing MS/MS screening programs. "One issue is to get national databases to gather data on these low prevalence disorders," says Harry Hannon, chief of CDC's clinical biochemistry branch. Scott Grosse, the program analyst who also worked on this report, explains, "One of the recommendations ... is the need to collect outcome data--to track the children who are identified, and track their health and evaluation data." MS/MS can screen for a large number of amino acid disorders (such as phenylketonuria), fatty acid oxidation disorders (such as medium-chain acyl-CoA dehydrogenase deficiency), and other organic acid disorders that can cause serious disabilities or death. All told, MS/MS can screen for about 20 metabolites in a single, two-minute run, but a combination of sophisticated technology and high implementation costs results in a variety of standards and availability throughout the country. The CDC plans a follow-up meeting in the fall.