Clinical and Laboratory Standards Institute document C57—Mass Spectrometry for Androgen and Estrogen Measurements in Serum is intended to aid the laboratorian in developing appropriate procedures for the use of mass spectrometry (MS) in the measurement of androgens and estrogens. The primary objectives of this document are to provide guidance and establish uniform practices necessary for producing quality data for quantitation of androgens and estrogens. The guideline provides details specific to androgen and estrogen measurement procedures with respect to preexamination (preanalytical) considerations, MS technologies, measurement procedure and run validation, as well as postexamination (postanalytical) considerations.