The purpose of this study is to make Erwinase available to patients with acute lymphoblastic leukemia (ALL) who have had previous allergic reactions to certain formulations of L-asparaginase.

Inclusion Criteria:

• Patient must give written informed consent to receive Erwinase.
• Patient must be treated for acute lymphoblastic leukemia.
• Patient must have either systemic hypersensitivity reactions to native (Elspar) or pegylated E.coli asparaginase (Oncaspar). This includes patients with generalized rash with or without anaphylactic symptoms, or patients with previously documented local or systemic reactions to E.coli derived L-asparaginase.

Exclusion Criteria:

• Previous allergic reaction to Erwinia L-asparaginase (Erwinase)
• Previous acute pancreatitis
• Pregnant or lactating woman