We report a 15-year-old boy diagnosed with acute lymphoblastic leukemia (ALL) in 1983. Induction therapy included L-asparaginase. After the second dose of L-asparaginase, he had a left sided focal seizure and computed tomography (CT) scan of the head showed a right frontal infarct. No further L-asparaginase was given. Complete remission was achieved and he successfully completed therapy in 1986. Eight months later he had an isolated bone marrow relapse. Reinduction therapy included L-asparaginase. After the fourth dose of L-asparaginase, he presented with severe headache and a CT scan showed a right temporal infarct. Repeat infarction on rechallenge with L-asparaginase has not been previously reported. Prophylactic therapy, such as fresh frozen plasma, should be considered before patients, with a previous cerebral insult, are rechallenged with L-asparaginase. However the effectiveness of such therapy has not been established.