The interaction between the immune and endocrine systems has recently been investigated. Hodgkin's disease represents a model of immune disturbance frequently associated with endocrine impairment. The present study evaluated the effect of the acute administration of beta-interferon or thymopentin on plasma growth hormone, prolactin and cortisol levels in children with Hodgkin's disease (N = 8) and age- and sex-matched healthy controls (N = 8). beta-interferon (1,000,000 IU), thymopentin (50 mg) or placebo (saline) were injected after two basal blood samples (-15 and 0) and further samples were drawn at 15, 30, 45, 60, 90 and 120 min. Plasma growth hormone, prolactin and cortisol levels were measured by specific RIAs. Plasma prolactin levels did not show significant change following beta-interferon or thymopentin injection in either the controls or the patients. In the patients with Hodgkin's disease, beta-interferon injection induced a significant increase in both plasma growth hormone and cortisol levels, while thymopentin was not effective. In controls both thymopentin and beta-interferon administration increased plasma growth hormone and cortisol levels. These results indicate that beta-interferon and thymopentin are immune substances active on the release of growth hormone and cortisol in healthy children. The lack of effect of thymopentin in children with Hodgkin's disease suggests an impairment of the immune-endocrine interaction in these patients.