The Analytical Reference Service conducted by the Sanitary Engineering Center has as its primary goal the evaluation of laboratory methods in the field of sanitary engineering. The Reference Service itself is a voluntary association of member organizations responsible for the conduct of laboratory programs. The evaluations are obtained by the cooperative efforts of the members in the analysis of identical samples. The sample Type I-A has the same composition as the original sample Type I (Minerals) and has been offered at the request of a number of the Analytical Reference Service members. Observations on the results of the Type I sample suggested that certain techniques were superior in their application to specific determinations.