Increases in CSF-1 levels in the period between leukemogenic induction and development of RI-AML. Following leukemogenic treatment, mice were individually bled at 2-month intervals for 12 months until the appearance of overt leukemia. Mice that developed RI-AML were separated into six groups depending on their latency period. Mean CSF-1 levels at death and for the 2-month intervals before death are shown for each latency period. The number of mice within each latency period is indicated in parentheses. *CSF-1 concentrations that are significantly different from 2-month posttreatment levels (Student's t-test, P < .05).