The study sent samples of typical case specimens to about 100 laboratories for analysis. The laboratories were willing to participate in this program, and satisfactory analytical results were obtained. In particular, there was a low incidence of false positives. However, the quantitative determination of drugs and metabolites, other than ethanol, showed wide interlaboratory variation. Moreover, there were some positive responses for low concentrations of secobarbital and opiate narcotics in blood, despite the immunoassay procedures available for screening these compounds in blood samples. Study data and graphs are included, and laboratory forms and reports are appended. Sixteen references are also appended. (Author summary modified)