1. A case of chronic thrombocytopenic purpura has been presented in which the pathogenesis appears to be due to congenital deficiency of a platelet-stimulating factor. 2. The factor exists in normal plasma and is stable on storage under normal blood banking conditions and on freezing. 3. The factor appears to act by stimulating megakaryocyte maturation and platelet production in an orderly and sequential manner.

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In a group of 1770 children with acute leukemia, treated in 11 pediatric centers associated with Children's Cancer Group A, surgical data was related to age at diagnosis, morphological type, the leukocyte count at onset, and the year of diagnosis. The age distribution was different in the 3 morphological types of childhood leukemia. A peak at the age 2 to 3 years, with a broad base extending from 2 to 5 years, was characteristic of acute lymphoid leukemia, while the peak was absent in other morphological types. The age distribution was similar in Caucasian and Negro children. The most favorable prognosis was found in children with acute lymphoid leukemia who were 2 to 6 years of age at diagnosis in whom the leukocyte counts were below 4,000/mm3 at onset. Progress in extending the median survival time of all children with acute lymphoid but not other types of leukemia was noted between 1957 and 1964. The 10% survival figure improved for all types of leukemia during this period.