Initial and serial serum copper levels (SCL) and erythrocyte sedimentation rates (ESR) of 29 children with Hodgkin's disease were reviewed to determine the relationship of these features to disease activity. Only six of 10 patients who relapsed had SCL greater than adult upper normal levels. Although correction for age increased this to 7, it also increased the number of patients with false positive results to 9 of 19. Although 9 of the 10 patients at relapse had an increase in SCL over the preceding value, almost one-fifth of patients in remission had increases in consecutive SCL greater than the average increase of patients who relapsed. We conclude that SCL, even when age corrected and consecutively followed, are not useful as indicators of disease activity in children with Hodgkin's disease. Although the ESR increased to greater than 20 mm/hour in 9 of 10 patients who relapsed, this determination could not be considered a useful early indicator of disease recurrence since it was so frequently elevated in patients who were free of disease (62 of 109 determinations). The extremely nonspecific nature of SCL and ESR in childhood renders these tests unreliable, particularly in the individual child.