Objectives To investigate patients with acute lymphoblastic leukemia (ALL) for TEL/AML1 fusion, BCR/ABL fusion, MLL gene rearrangements, and numerical changes of chromosomes 4, 10, 17 and 21 by fluorescence in situ hybridization (FISH) and to determine the relationship and the significance of those findings.Methods Fifty-one American patients (34 men and 17 women) were included in this study. Of them there were 41 patients with pro-B cell type ALL, 9 with B cell type ALL and 1 with T cell type ALL. Chromosome metaphases of each sample were prepared according to standard protocols. Fluorescence in situ hybridization was performed using commercially available DNA probes, including whole chromosome painting probes, locus specific probes, specific chromosome centromere probes and dual color/multiple color translocation fusion probes. The digital image analysis was carried out using Cytovision and Quips FISH programs.Results An overall incidence of chromosomal anomalies, including t (9; 22), MLL gene rearran Objectives To investigate patients with acute lymphoblastic leukemia (ALL) for TEL / AML1 fusion, BCR / ABL fusion, MLL gene rearrangements, and numerical changes of chromosomes 4, 10, 17 and 21 by fluorescence in situ hybridization Relations and the significance of those findings. Methods Fifty-one American patients (34 men and 17 women) were included in this study. Of them there were 41 patients with pro-B cell type ALL, 9 with B cell type ALL and 1 with T cell type ALL. Chromosome metaphases of each sample were prepared according to standard protocols. Fluorescence in situ hybridization was performed using commercially available DNA probes, including whole chromosome painting probes, locus specific probes, specific chromosome centromere probes and dual color / multiple color translocation fusion probes. The digital image analysis was carried out using Cytovision and Quips FISH programs. Results An overall incidence of chromosomal anomalies, including t (9; 22) , MLL gene rearran