Patients will receive four injections of the immunotoxin. The immunotoxin is designed to selectively destroy myeloid leukemia cells. The injections will be given through a vein twice weekly for two weeks. Patients will then be evaluated twice weekly for the next two weeks. If there has been improvement in the leukemia, or if the leukemia has remained stable and there have been no serious side effects of treatment, patients will then receive a second course of immunotoxin injections. These will again be given twice weekly for two weeks. Depending on the effectiveness against leukemia and the side effects, patients may receive maintenance treatment. This would also consist of two weekly injections given for two weeks followed by two weeks of observation. Maintenance therapy may continue for up to four months for partial response and up to two months for complete response.