To evaluate the clinical safety of different doses of MEDI-507 through day 33.

To evaluate the pharmacokinetic characteristics of MEDI-507 given in dose intervals.

Inclusion Criteria:

• Renal allograft recipients receiving their first or second allograft
• Age over 18
• Maintained on conventional immunosuppression
• Completed informed consent document

Exclusion Criteria:

• Known hypersensitivity to MEDI-507
• More than two renal allografts
• Moribund and unlikely (in the opinion of the investigator) to survive the duration of the trial
• Simultaneous use of other investigational agents (this does not include the use of licensed agents for indications not listed in the package insert)
• Any of the following clinical settings or diagnoses posttransplant:

pregnancy or nursing mother: Ø Human Immunodeficiency Virus infection Ø hemodialysis or chronic peritoneal dialysis Ø use of a ventilator Ø hyperacute rejection

• Having received OKT3, tacrolimus, or antilymphocyte globulin during the current allograft
• Less than 10 ml/hr average urine output over 4 hours since the end of surgery