IN AN 18-MONTH PERIOD, 340 consecutive adult patients with acute leukemia were treated using a 7-day continuous infusion of Ara-C in combination with rubidazone, vincristine and prednisone (ROAP). Of 334 (96%) evaluable cases, 77% were 50 years of age or older. The complete remission (CR) rate was 51% with a standard error of 3%. After adjustment for known prognostic factors this overall CR rate is 10% higher than the predicted CR rate when compared to the last completed SWOG study which used adriamycin in combination with a similar regimen of Ara-C, vincristine, and prednisone. The CR rate in patients over 50 years of age was particularly noteworthy. Using rubidazone, the CR rate was 46.1% (116/256) compared to 37.4% (91/243) for the adriamycin study in this poorly responding age group. The median survival time achieved was 27 weeks. However, in the age groups 40–49 years and 50–59 years the median survival was 70 and 44 weeks, respectively.