Inclusion Criteria:

- adult patients, 18-80 years of age;

- histological diagnosis of primary central nervous system lymphoma;

- B-cell proliferation verified by positive staining for CD20;

- >=1 measurable lesion.

Exclusion Criteria:

- prior chemotherapy, other than corticosteroids, >=6 weeks before and after diagnosis
or surgery;

- history of prior cranial irradiation;

- evidence of plurisystemic non-Hodgkin's lymphoma;

- other active malignant disease (other than basal cell or squamous cell cancer of
skin,or cancer in situ of cervix;

- uncontrolled active infection.