Oxytocin is a peptide consisting of nine amino acids that acts as a neurotransmitter in biological systems. It is known for its roles during and after childbirth, however, it is also the focus of many research projects investigating treatment of disorders such as depression and autism. As such, the concentration of oxytocin found in patient serum is often of interest. Presented here is a method for analysis of oxytocin in serum samples using the Hitachi Chromaster HPLC with diode array detection.