We report clinical, immunologic, and cytogenetic characteristics of six patients with a t(1;19)(q23;p13) that was balanced in one case and of the unbalanced type [-19,der(19)t(1;19)(q23;p13)] in the remaining five cases. Intracytoplasmic immunoglobulins (cIg) were positive in the three cases where they were found. We also report on another patient, with a t(17;19) involving 17q11 and probably 19q13 regions, although involvement of 19p13 could not be excluded. In this patient, cIg were also present, thus raising the issue of whether such a rearrangement could be a variant of t(1;19). Clinically, five patients belonged to the high-risk acute lymphoblastic leukemia (ALL) group, because of high leukocytosis, central nervous system (CNS) disease at presentation, or massive organomegaly. Cytologically, all cases were FAB type L1. Except for the two cases allografted in the first complete remission (CR) all patients relapsed, three of them within 13 months. Two CNS relapses were seen in spite of adequate CNS prophylaxis. ALL with t(1;19) appears to be a poor-risk ALL subgroup and probably requires a reinforcement of therapeutic modalities that might include, when possible, allografting at first CR.