We report on the finding of a t(1;17) in two primary neuroblastomas. Subsequent fluorescence in situ hybridization (FISH) analysis revealed the presence of 1; 17 transfocations in four out of nine neuroblastoma cell lines. The chromosome 1 short arm breakpoints were determined using region-specific probes. FISH screening also demonstrated or confirmed the presence of 11;17 translocations in three cell lines and other chromosome 17 rearrangements in those cell lines that did not carry a t(1; 17) or t(11; 17). Our data extend previous cytogenetic findings and suggest that, in addition to the known involvement of chromosome I, one or more genes on chromosome 17 also play a role in neuroblastoma development. Genes Chromosom Cancer 10:103–114 (1994). © 1994 Wiley-Liss, Inc.