The present investigation was motivated from the consideration that a host environment rich in iron, represented by high serum transferrin saturation (TS) and high serum iron and serum ferritin levels might offer favorable growth conditions for leukemic cells in addition to infection, thus affecting survival. Serum measurements were obtained on 113 pediatric patients with acute lymphoblastic leukemia (ALL), seen at Memorial Sloan-Kettering Cancer Center between May 20, 1981 and August 8, 1983. A significant difference (p less than 0.001) was found between the survival of patients according to whether their first measured TS was greater than 36% or less than 36%, with fewer deaths in the group with TS less than 36. The relationship between TS and survival was still observed when patients were stratified according to length of time from diagnosis, risk group, French-American-British (FAB) classification, or presence of organomegaly at diagnosis (p less than 0.001). Similar differences were observed between survival of patients grouped according to their first measured serum ferritin. These results independently confirm and extend observations presented earlier and support the consideration that motivated this study. The value of serum iron-related measurements as prognostic variables cannot be established from this type of study; however, these findings suggest the need for a prospective study.