OUTLINE: This is a dose escalation, open label study. Patients are stratified by age (pediatric vs adult). Patients receive arsenic trioxide IV over 1-2 hours once daily for 3 consecutive days then once weekly for 5 weeks. Patients with stable or responding disease receive additional courses of therapy every 8 weeks for up to 1 year in the absence of disease progression or unacceptable toxicity. Patients receive escalating doses of arsenic trioxide until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose preceding that at which 2 or more patients out of 6 experience dose limiting toxicity. Patients are followed for at least 1 month after treatment.