The purpose of this trial is to determine the safety of a 90Y-radiolabeled, humanized (CDR-grafted) form of the LL2 monoclonal antibody in patients with Non-Hodgkin's lymphoma (NHL) at different dose levels.

Inclusion:

• Histological or cytological diagnosis of B-cell lymphoma, and has failed at least one regimen of standard chemotherapy. (All histological grades of NHL will be eligible for this trial.)
• Measureable via CT, with at least one lesion > or = 1.5cm in one or both dimensions. (Splenic tumors in absence of other tumors will not qualify.)
• Radiological studies (ie - CT) must be performed within 4 weeks prior to study start.
• Acceptable tumor burden that will allow adequate follow-up and evaluation.
• Less that 25% bone marrow involvement, determined by bone marrow biopsy.
• Must observe the following washout periods:

At least 4 weeks beyond any major surgery. At least 4 weeks beyond any radiation therapy to the index lesion, and has recovered from radiation-induced toxicity.

At least 4 weeks beyond chemotherapy and/or immunotherapy. At least 2 weeks beyond corticosteriod(s) use and blood counts are with laboratory criteria.

• Must have Karnofsky score >70% (or equivalent, ECOG 0-2) with expected survival of at least 6 months.
• Serum creatinine < or = 1.5mg/dl or creatinine clearance > or = 50ml/min.
• Serum bilirubin < or = 2mg/dl.
• Hemoglobin > or = 10 g/dl; WBC > or = 3000/mm3; granulocyte count > or = 150/mm3; platelet count > or = 100,000/mm3 with out transfusions or cytokines for at least 30 days prior to study.
• Immunomedics ELISA assay of HahLL2 < 100ng/ml for those with prior history of monoclonal antibody infusions.
• Cognizant informed consent.