Inclusion Criteria:

- Age 18-70 years

- B-ALL (OMS) with >=20% of blasts in bone marrow

- CD22+ expression >=70% of the blast population

- All previously treated ALL patients who have experienced relapse or treatment failure

- At least 15 days since previous treatment

- Performance status 0 - 2

- Creatinine clearance >= 50 ml/min (Cockroft formula).

- Serum bilirubin <= 30 mmol/l

- Written informed consent

Exclusion Criteria:

- T-ALL

- Meningeal involvement

- CD22 expression on tumor cells or < 70%

- HIV positive

- Active Hepatitis B or C

- Active infection within 7 days of starting treatment

- Left ventricular ejection fraction < 50%.

- Contra-indication to 90Y-DOTA-hLL2

- Previous or concurrent second malignancy except for adequately treated basal cell
carcinoma of the skin, curatively treated in situ carcinoma of the cervix, curatively
treated solid cancer, with no evidence of disease for at least 5 years

- Any psychological, familial, sociological or geographical condition potentially
hampering compliance with the study protocol and follow-up schedule

- Participation at the same time in another study in which investigational drugs are
used

- Absence of written informed consent