The implantation traces of early embryonal death and abortion in rats induced by some drugs were studied. Early embryonal death and abortion were caused by intraperitoneal injection of 15 mg/kg of busulfan on the 7th day of gestation or 40 mg/kg of 6-mercaptopurine on the 7th and 8th day of gestation. The observation period and staining of the implantation traces were investigated. Early dead embryos and placentas were delivered between the 20th and 24th day of gestation. These were eaten by the dams. The implantation traces of abortion or early embryonal death, and those of normal delivery were able to be identified up to the 120th day and 500th day after extraction, respectively. The implantation traces of abortion were smaller in the three experimental groups. All kinds of implantation traces were stained distinctly with 10% ammonium sulfide, 0.2% sodium hydroxide and 2% potassium ferrocyanide. In this staining method, sodium hydroxide has an excellent effect on the staining of implantation traces. Specimens washed in water after being stained with sodium hydroxide and fixed in formalin can be preserved without discoloration for a long period of time.