The introduction of antimetabolites and steroid hormones has resulted in an appreciable increase in the survival time of patients with acute stem-cell leukemia of childhood. The occurrence of prolonged remissions, extending in some cases over a period of several years, has permitted observations concerning the course of the disease, the development of formerly unknown or rare complications, and the response to varied therapeutic regimens which, in our present state of ignorance, may well provide clues for future investigations. In particular, a comparison of long-term survivors with less favorably responding patients should be of interest. Such a study has not been attempted before, although several recent articles1-4 deal with the therapeutic results achieved with the newer agents. Case Material The analysis deals with an unselected group of 169 children in whom an unequivocal diagnosis of acute stem-cell leukemia could be made on the basis of peripheral blood findings, supported in