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.