Serum copper and zinc levels, and Cu/Zn ratio were measured in 40 children with Hodgkin's (n = 18) and non-Hodgkin's (n = 22) lymphomas, and 30 controls using Atomic Absorption Spectrophotometry. The mean serum copper levels were higher in lymphoma patients than in controls (199.8 micrograms/dl v. 95.8 micrograms/dl) P < 0.001). The increase in serum copper level correlated with the stage of disease being maximum in Stage IV (219.4 micrograms/dl v. 143.2 micrograms/dl) (P < 0.01). On the other hand, there was a decrease in the serum zinc levels in lymphoma patients as compared to controls (86.1 micrograms/dl v. 117.4 micrograms/dl) (P < 0.001), but this was significant only in patients with advanced disease. The Cu/Zn ratio was therefore markedly increased in these patients (2.46 v. 0.83) (P < 0.001). Following successful treatment the abnormal serum copper and zinc levels returned towards normal. The exact mechanisms responsible for these alterations are yet to be elucidated. We conclude that serum copper and zinc levels and Cu/Zn ratio are easily measurable biochemical indices that can be used as predictors of successful treatment in pediatric patients with lymphomas.