Chromosomal analyses of three pheochromocytomas from patients with von Hippel-Lindau syndrome are reported. One pheochromocytoma revealed a normal karyotype, another tumor showed a trisomy 7 as the only chromosomal abnormality, whereas in a further sample a polyclonal chromosome constitution was detected. In addition to a normal 46,XX cell line, four distinct chromosomally abnormal cell lines could be identified. One cell line revealed partial trisomy for the long arm of chromosome 1 and additionally exhibited the phenomenon of telomeric association. Most interestingly, three further cell clones showed rearrangements of chromosome 3 including the region where the von Hippel-Lindau gene was mapped; three rearrangements resulted in a partial or total trisomy of 3p. Our findings are discussed in relation to previously reported cytogenetic and molecular results regarding von Hippel-Lindau syndrome.