Prostaglandin E (PGE) production was evaluated in 18 normal subjects and 29 patients with Hodgkin's and non-Hodgkin's lymphomas. Plasma PGE levels of patients were found to be highly increased. Increased PGE synthesis was demonstrated in conditioned media from peripheral blood and bone marrow mononuclear cells, arising from the adherent cell fraction enriched in monocytes. No relationship with clinical or pathological findings was observed.