Comparative genomic hybridization (CGH) was used to detect chromosomal imbalances in tumor DNA from two relapsed samples obtained in stages II and IV of a T-cell non-Hodgkin lymphoma in order to identify genetic mechanisms involved in tumor progression of this neoplasm. With conventional cytogenetic techniques (CCT), a complex hyperdiploid karyotype was obtained in stage IV. Using CGH analysis, a normal profile was observed in stage II, whereas gains of 6p11.2, 7q11.2, 7q21-->q32, 7q34, 10p13, Xp11.4, and loss of 4q33-->qter chromosomal regions were detected in stage IV.