Antigen stimulation may lead to expansion or deletion of T-cells expressing T-cell receptors that belong to specific V beta gene families. Since such stimulation at the same time will lead to conversion from naive to memory T-cells, we have asked whether a bias in V beta families can be observed when comparing these two populations. We have studied the expression of V beta 3, 8, 13.3, 19, and 22 in peripheral blood T-cells for 12 apparently healthy male donors. For flow cytometry 100,000 CD4+ or CD8+ cells each were analysed in three-colour immunofluorescence for percentage of V beta families among CD45R0- naive and CD45R0+ memory cell. Greater than twofold excess was found in the CD8+CD45R0+ cells in four cases (1 x V beta 13.3, 2 x V beta 19, 1 x V beta 22) and a greater than twofold decrease in CD8+CD45R0+ cells in two cases (1 x V beta 8, 1 x V beta 22). In contrast, among CD4+ cells no such bias was detected. The excess in CD8+CD45R0+ memory cells showed no substantial fluctuation over time in that it was found to be stable for 19 to 70 days. Finally, in vitro conversion of purified CD8+CD45R0- cells to CD45R0+ cells by polyclonal stimulation with PHA did not result in the excess of V beta usage observed in vivo. These data suggest that specific antigen stimulation during past infection or allergy may be responsible for the excess of certain V beta gene families. Clinical studies looking for disease associations will have to test CD4 and CD8 naive and memory subsets in order to precisely identify a bias in V beta usage and these studies will have to consider the pronounced changes observed in healthy controls.