To evaluate whether HSCT from matched family or unrelated donors (MD) is equivalent to the HSCT from matched sibling donors (MSD). To evaluate the efficacy of HSCT from mismatched family or unrelated donors (MMD) as compared to HSCT from MSD/MD. To determine whether therapy has been carried out according to the main HSCT protocol recommendations. The standardisation of the treatment options during HSCT from different donor types aims at the achievement of an optimal comparison of survival after HSCT with survival after chemotherapy only. To prospectively evaluate and compare the incidence of acute and chronic GvHD after HSCT from MSD, from MD and from MMD.

Inclusion Criteria:

all patients with ALL (except for patients with B-ALL) who fulfil the following criteria:

• age at time of initial diagnosis or relapse diagnosis, respectively

  ≤18 years

• indication for allogeneic HSCT

• complete remission (CR) is achieved before SCT

• written consent of the parents (legal guardian) and, if indicated, the minor patient via "Informed Consent Form"

• no pregnancy

• no secondary malignancy

• no previous HSCT

• HSCT is performed in a study participating centre.

Exclusion Criteria:

• not signed inform consent of the parents (legal guardian)
• pregnancy
• secondary malignancy
• previous HSCT