A whole blood culture technique was used to establish conditions for stimulating the production of cytokines by cord blood lymphocytes. The cultures were stimulated with mitogens (concanavalin A and phytohaemagglutinin) and allergens (beta-lactoglobulin (BLG), ovalbumin (OVA) and house dust mite (Der p 1)) at a range of concentrations. Interleukin (IL-) 2, IL-4, IL-10, IL-13 and interferon-gamma (IFN-γ) concentrations were assayed in the supernatants at 24, 48 and 72 h. Stimulation with mitogens but not allergens induced increases in IL-2 and IL-13 concentrations. IFN-γ was strongly induced by mitogenic stimulation: maximal responses were seen at 48 h. Stimulation with the allergens also induced an increase in IFN-γ concentration which was maximal for 100 μg/ml of BLG and OVA. Der p 1 induced the highest IFN-γ production among the allergens. IL-4 concentrations were increased in mitogen and Der p 1 stimulated cultures. This was maximal at 48 and 24 h, respectively. IL-10 was induced with mitogen and allergen stimulation. Thus, this study has established conditions for assessing production of lymphocyte-derived cytokines in a simple whole umbilical cord blood culture system.