The list of physiological events in which sex steroids play a role continues to increase. To decipher the roles that sex steroids play in any condition requires high quality cohorts of samples and assays that provide highly accurate quantitative measures. Liquid and gas chromatography coupled with mass spectrometry (LC-MS and GC-MS) have dramatically increased the capability to quantitatively measure sex steroids in complex biologic samples. Although it is important to optimize and calibrate the LC-MS and GC-MS steps, other areas such as sample preparation, molecular derivatization, and data analysis need to be carefully considered to minimize assay variation. The specific steps necessary for an effective quantitative assay are highly dependent on the type of sex steroid(s) being measured and the analytical steps described in this article will not be pertinent to every analyte. In this article, however, many of the steps necessary to develop an effective assay for sex steroids will be reviewed with a focus on areas that contribute to variation within the final quantitative results. The development of robust quantitative assays with high precision, accuracy, and reproducibility will continue to contribute to our understanding of the specific roles sex steroids play in diseases such as cancer. (Contains 1 figure and 1 scheme.)