The purpose of this study is to determine the safety and feasibility of unrelated double umbilical cord blood units Transplantation in patients with haematological malignancies using Antithymocyte Globulin Cyclophosphamide, busulfan as conditioning and cyclosporin, methylprednisolone as GVHD prophylaxis.

Inclusion Criteria:

• Hematologically & Histologically confirmed acute lymphoblastic or acute and chronic myeloid leukemia in Remission
• Aged 1 year to 50 years
• Absence of HLA compatible related or other related donor.
• Availability of suitable UCB units.
• karnofsky performance score (> 12 yr) or lansky play performance(<12 yr) : 80- 100
• Adequate renal function defined as:Serum creatinine <1.5 x normal,
• Adequate liver function defined as:Total bilirubin <1.5 x normal, or SGOT (AST) or SGPT (ALT) <3.0 x normal
• Adequate cardiac function defined as: Ejection fraction >50% by echocardiogram.
• Adequate pulmonary function defined as:Uncorrected DLCO 50% by pulmonary function test.For children who are uncooperative, no evidence of dyspnea at rest, no exercise intolerance, and a pulse oximetry >94% on room air

Exclusion Criteria:

• Age: < 1year or > 50 year
• Patients with an available 5-6/6 HLA-A, -B, -DRB1 matched sibling or other related donor
• karnofsky performance score (> 12 yr) or lansky play performance(<12 yr) < 80
• HIV positive patients.
• Female patients who are pregnant or breast feeding
• Life expectancy severely limited by diseases of vital organs other than the disease indication for transplant
• Serious concurrent untreated infection e.g. active tuberculosis, mycoses or viral infection
• Serious psychiatric/ psychological disorders
• Absence of /inability to provide informed consent
• Clinical or Paraclinical evidence of CNS or PNS involvement