The time period covered by this review is the Chemical Abstracts citation dates October 1, 1996, to October 1, 1998. References cited in this review are drawn from the world literature and are limited to the analysis of human fluid and tissues. Chemiluminescence (CL) (light emission produced in a chemical reaction from the decay of chemiexcited species to the electronic ground state) and bioluminescence (BL) (light emission found in nature) have continued to find diverse applications in analysis but only chemiluminescence has become an established technique in routine clinical chemistry.The Proceedings of the ninth International Symposium on Bioluminescence and Chemiluminescence (B1) and a series of review articles (B2-B10) describe recent advances in the analytical applications of CL and BL. The regular literature survey in the Journal of Bioluminescence and Chemiluminescence also provides information on the fundamental and applied aspects of both CL and BL (B11-B14). A survey of commercially available luminometers and imaging devices for low-light level measurements and kits and reagents utilizing BL and CL has been updated (B15).New Reagents and Analytical Reactions. A range of new reagents have been developed for clinical assays and these include CL immunoassay labels such as acridinium esters (B16, B17) and nucleophilic polysubstituted acridinium esters (B18), di-o-bromophenylacridinium esters for use as detection reagents in an amplification cascade immunoassay (alkaline phosphatase label) (B19), acridinium esters for dual-label strategies (B20), fluorene derivatives for enhancing the CL detection of glucose oxidase labels (B21), and pyrylium compounds for detection of doublestranded DNA (B22). Further examples of 1,2-dioxetane derivatives (B23-B26), imidazopyrazinone CL superoxide probes (B27), a range of luminol and isoluminol reagents, including N-(βcarboxypropionyl)luminol (B28) and dimethylisoluminol (B29), and acridine derivatives (B30) have been described.Additional examples of enhancers for CL detection reactions for horseradish peroxidase (HRP) labels have been developed, e.g., phenothiazines (B31), aromatic amine and hydroxy compounds (B32), and boronates (B33, B34). Thiourea enhancers for CL lucigenin reactions (B35) have also been described. Sensitive analytical reactions for β-galactosidase are available using 1,2-dioxetane derivatives or 5-bromo-4-chloro-3-indolyl-β-D-galactopyranoside (X-gal) (3 amol/assay) (B36). A mutant of Photinus pyralis luciferase (modification of residue 245) with a 5-fold increased K m for ATP has been produced and this improved reagent is useful in ATP assays (B37).Clinical Assays. CL methods continue to be applied to the analysis of body fluids and tissues for clinically important analytes (detection limit): enzymatic-based analysis of apoptotic DNA using CDP-Star (B38), serum oxalate using a coupled oxalate oxidase