 Patients receive rituximab IV followed, no more than 4 hours later, by indium In 111 ibritumomab tiuxetan for imaging IV over 10 minutes on day 1. If biodistribution is acceptable, patients receive rituximab IV followed, no more than 4 hours later, by a single dose of yttrium Y 90 ibritumomab tiuxetan IV over 10 minutes on day 7, 8, or 9 in the absence of disease progression or unacceptable toxicity. 