Fertilization failure occurs in 1–5% of ICSI cases. An abnormality of the oocyte activating ability of spermatozoa is one of a major causes of fertilization failure. For such cases, artificial oocyte activation (AOA) is expected as a method of treating for fertilization failure after ICSI. There are various methods of AOA combined with ICSI. We have adopted treatment with calcium ionophore, A23187, which is a commonly used method, and here, we report on the present status of the methods of oocyte activation combined with ICSI that we use. Although AOA with electrical technique or chemicals stimulation is clinically performed, the safety of this has not yet been proven, and the safer effective methods of AOA are desired.