Inclusion Criteria:

- proven diagnosis of ALL or very aggressive Non-Hodgkin-Lymphoma
(Burkitt/Burkitt-like) and CNS relapse

- CNS involvement demonstrated by a positive ventricular or lumbar CSF cytology or
characteristic signs and symptoms of neoplastic meningitis plus an MRI or CT scan
indicating the presence of meningeal involvement

- in combined relapse in CNS and other locations: systemic therapy with CNS active
drugs can be postponed for at least 2 weeks

- Karnofsky Performance Score is > or = 60%

- 18 years of age or older

- free of uncontrolled infection

- recovered from any grade III / IV toxicities attributable to prior treatment with the
exception of hematotoxicity

- patient not pregnant or breast feeding and effective methods to prevent pregnancy

- free from severe heart, lung, liver or kidney dysfunction

- written informed consent

Exclusion Criteria:

- failed to respond (as defined by no clearance of the CSF) to > 1 dose of prior i.th.
MTX or ARAC or triple therapy

- history of neurotoxicity (grade III - IV) attributed to i.th. or systemic HD therapy
with MTX or ARAC

- prior CNS relapse < 1 month before