Mindfulness-Based Stress Reduction (MBSR) or other forms of meditation have been found to decrease blood pressure, improve sleep, decrease anxiety and stress, decrease cortisol, induce the immune response, and produce other health benefits. However, the mechanism of action of meditation’s beneficial effect on health is uncertain. The peptide neurohormone oxytocin is generally considered to have anti-stress effects, and like meditation, also decreases anxiety and blood pressure, cortisol and induces the immune response. In addition, oxytocin, like meditation, has been associated with improvement in cardiac risk factors such as hypertension, insulin resistance, and decreased heart-rate variability. Our hypothesis is that oxytocin may partially mediate the beneficial effects of meditation, and this experiment is designed to measure whether oxytocin levels increase with a meditation task. Twenty experienced meditators will be drawn from a community sample of individuals with extensive training and practice in insight meditation/mindfulness meditation (daily meditation for at least 3 years, and to have attended at least 1 week-long insight meditation retreat). Twenty age-matched controls will be recruited using community advertisements. Study participants will be admitted to the MGH General Clinical Research Center, where a research nurse will insert an IV catheter into the forearm vein of the participant. Blood samples will be taken at rest, during a meditation exercise, and during a control exercise. Participants will also complete questionnaires regarding stress levels, mindfulness concentration, and other psychological measures. Blood samples will be assayed for oxytocin using radioimmunoassay or enzyme-linked immunosorbent assay.