Four hundred and fifty pregnant women were recruited for termination of early gestation by mifepristone combined with dl-15-methyl PGF2 alpha or misoprostol. Eight-four out of 450 subjects received curettage because of heavy or prolonged vaginal bleeding and slow decline of urinary hCG levels. Histopathology examinations of specimens obtained during curettage revealed denatured, necrotic and obscure villi and trophoblasts in 77 specimens, which accounted for 91.7%. Among them, 68 samples were mingled with inflammatory cell infiltration, and 15 with decidual cells, only 3 were villi and trophoblasts alone. The remaining 7 specimens were decidua in 6 and inflammatory infiltration in 1, which accounted for 7.1% and 1.2% respectively. This study suggested that the major cause resulting in heavy or prolonged vaginal bleeding after medical abortion by mifepristone and prostaglandin analogue was residual villi and trophoblasts with inflammatory cell infiltration.