Vanadium salts have been shown to be aneuploidogenic in human lymphocyte cultures. In particular, increases in the frequency of chromosome satellite associations and a high proportion of induced micronuclei with centromeric signals seem to be connected with chromosome malsegregation mechanisms in which acrocentric chromosomes may be involved. Our aim was to assess the contribution of these chromosomes to the formation of vanadium-induced micronuclei by applying the fluorescence in situ hybridization technique to the human lymphocyte micronucleus assay. Whole blood cultures were treated after 24 h with 0, 10, 40, and 80 microM sodium orthovanadate or vanadyl sulfate and harvested at 72 h; vinblastine, 20 ng/ml, was used as a reference compound. The slides were then hybridized with biotin-labeled beta-satellite DNA probes specific for all human acrocentric chromosomes. After chemical treatment, the percentage of micronuclei with fluorescent signals was found to be statistically higher than that in control cultures, whereas vinblastine induced only a slight increase in micronuclei.