The genes coding for TCR alpha and delta chains share the same genetic locus (TCRA/D). The rules governing the utilization of a V gene with the alpha and delta chains have not been established. More specifically, it is not known whether the position of a gene within the locus influences its utilization in alpha and delta TCR. To elucidate these points, we mapped ADV2 genes in the TCRA/D locus of BALB/c mice and analyzed their utilization in TCR alpha and delta transcripts from thymi isolated from mice of different ages. Our results show that all ADV2 genes can be used by the two chains, but with strikingly different patterns. Moreover, ADV2 utilization by the alpha chain proceeds in successive concentric waves during development, suggesting a progressive regulation of gene accessibility and utilization. These results support independent control of TCRA and TCRD gene assembly.