Transgenic plants with Ds element distributed over different loci on chromosome 4 (Fig. 1) and the homozygous transformants with Ac transposase gene were established through Agrobacterium-mediated approach. In this study, the plants carrying Ds element from different loci were crossed with the plant carrying Ac transposase individually. The plants of F(1) generation carrying both Ds element and Ac transposase were used to produce the F(2) populations (Table 1). Analysis of the F(2) generation by the PCR method revealed that the excision frequencies of Ds element were higher in the telomeric region of chromosome 4 than in the centromeric region (Fig. 4). These results showed that the insertion site of Ds element has strong effect on its excision frequency. We suggest that the special construct of chromosome near the insertion site of Ds element is related to the excision frequency of the Ds element.