A method has been developed for measuring ginkgolide A, B, and bilobalide in ginkgo biloba L. extracts by using a self-assembled microdialysis device coupled on-line to high-performance liquid chromatography. The optimal conditions for dialysis efficiency and chromatographic analysis were investigated. The results show that the dialysis efficiencies for ginkgolide A, B, and bilobalide are 97.8-100.4%. For the spike concentration of 45 mg L(-1), the recoveries of ginkgolide A, B, and bilobalide in ginkgo biloba L. extracts were at 97-100.7% with 3.1-4.7% RSD. The proposed method has therefore been shown to be applicable to the analysis of ginkgolide A, B, and bilobalide in ginkgo biloba L. extracts.