Molecular luminescence spectroscopy, including fluorescence, phosphorescence, and chemiluminescence (CL), is among the most sensitive of analytical methods. Its use in clinical chemistry has been extensive since the late 1950s and is constantly expanding. Modern separation and immunoassay methods coupled with luminescence detection have revolutionized the detection and determination of endogenous substances, xenobiotics, and their metabolites. Newer techniques such as time‐resolved fluorimetry and phosphorimetry, detection by fiber‐optic sensors, and derivatization with infrared (IR)‐emitting dyes are expanding the range of clinical analysis into new realms of analytical selectivity, sensitivity, and expediency on a scale unimagined until recently. This article considers some of the aspects of fluorescence, phosphorescence, and CL spectroscopy that have contributed to important recent advances in clinical analysis.