Prostaglandin F2a (PGF2a) is one of the five primary prostaglandins derived enzymatically directly from the endoperoxide PGH2. PGF2a was initially discovered in seminal fluid, and to date the majority of the functional roles ascribed to it relate to fertility, pregnancy, and parturition. PGF2a is a potent luteolytic agent and is used to induce ovulation in domestic livestock. It is also a potent uterine stimulant, and is part of the cascade of myometrial stimulants which induce and sustain labor. PGF2a is rapidly metabolized to 13,14-dihydro-15-keto PGF2a in vivo, by the enzymes 15-hydroxy prostaglandin dehydrogenase and d13-reductucase.{310,1157,5442,387} Measurement of 13,14-dihydro-15-keto PGF2a in plasma can be used as a marker of the in vivo production of PGF2a.{878,1463} The Cayman Chemical 13,14-dihydro-15-keto PGF2a Enzyme Immunoassay is a competitive assay that provides measurements of 13,14-dihydro-15-keto PGF2a within the range of 2.3-5,000 pg/ml, typically with a detection limit (80% B/B0) of approximately 15 pg/ml. Although the tracer and antiserum for this assay have been sold separately for many years, the reagents are now combined with an accurate standard and packaged together in a convenient assay kit. The assay has been validated for the measurement of 13,14-dihydro-15-keto PGF2a in plasma, a common matrix for measurement of this PGF2a metabolite.{878}