The purpose of this study is to identify a well-tolerated, effective dose and schedule of AMG 531 for the treatment of Chemotherapy Induced Thrombocytopenia (CIT) in subjects with lymphoma receiving multi-cycle chemotherapy.

Inclusion Criteria:

• Histologically confirmed Hodgkin's lymphoma or Non-Hodgkin's lymphoma receiving Q14, Q21, or Q28 day CHOP, ICE, ESHAP, or DHAP chemotherapy; with or without Rituximab
• Has adequate bone marrow function; platelet count > 100 x 10^9/L on the day of initiation of the on study chemotherapy of the next treatment cycle and absolute neutrophil count, ANC > or = 1 x 10^9/L, and hemoglobin > or = 9.5 g/dL
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
• Has adequate liver function
• must be able to receive the same chemotherapy regimen during the first treatment cycle as was received during the prior qualifying cycle
• must experience Common Terminology Criteria (CTC) grade 3 or 4 thrombocytopenia (platelet count < 50 x 10^9/L) as a result of the chemotherapy administered in the cycle immediately preceding study entry
• has serum creatinine concentration < or = 2 mg/dl

Exclusion Criteria:

• More that 1 prior relapse chemotherapy regimen
• Sepsis, disseminated coagulation or any other condition that may exacerbate thrombocytopenia
• Significant bleeding (CTC grade 3 or 4)
• History of thromboembolic disease
• Subjects who are identified by clinical history and/or serological testing to have either acute or chronic hepatitis B or C infection or to be HIV positive
• Use of any nitrosourea or mitomycin-C
• Has received any thrombocytopenic growth factor
• Has received a marrow or peripheral blood stem cell infusion
• Known hypersensitivity to any recombinant E. coli-derived product