Cytogenetic findings obtained during the clinical course in two patients (one child and one adult) with Ph-positive acute lymphoblastic leukemia (ALL) are reported. Chromosomal abnormalities in addition to Ph chromosome were detected in both patients. At the beginning of the disease, such abnormalities consisted of the trisomy of chromosome 1 and monosomy of chromosomes 8 and 9, with a sub-line 45, X Y, Ph, -8 in the child; in the adult patient a hyperdiploid clone with 57–59 chromosomes and Ph duplication was present. At relapse, the same karyotypic anomalies reappeared in the child, whereas in the adult a high frequency of chromosomal rearrangements, such as ring and dicentric chromosomes, was observed after cranial irradiation. The occurrence of chromosomal abnormalities additional to Ph during the clinical course in ALL patients is discussed, taking into account data from the literature concerning the lymphoid blastic crisis in chronic myeloid leukemia patients.