The Oxytocin antiserum was quality control tested using standard immunohistochemical methods. The antiserum demonstrates strongly positive labeling of rat hypothalamus using indirect immunofluorescent and biotin/avidin-HRP techniques. Recommended primary dilutions are 1/200 - 1/400 in PBS/0.3% Triton X-100 - FITC and 1/4,000 - 1/8,000 in PBS/0.3% Triton X-100 - Bn/Av-HRP. Staining is completely eliminated by pretreatment of 1 mL of the diluted antibody with 5 µg of Oxytocin. Pretreatment of 1 mL of the diluted antibody with as much as 100 µg of vasopressin does not diminish staining.