Methylprednisolone shows a synergistic effect on viability with either daunorubicin or cytosine arabinoside. The combined effects of cytosine arabinoside and methylprednisolone and daunorubicin and methylprednisolone on cell viability in (A) Kasumi-1 cells at 3 days for daunorubicin and 5 days for cytosine arabinoside and in (B) SKNO-1 cells at 5 days, as determined by ATP level, is shown by isobologram. Synergy appears as points below the line of additivity. Experiments were performed in duplicate.