Using in vitro fertilization techniques, the processes and mechanisms of mammalian fertilization are being investigated. The guinea-pig and golden hamster have been used as major subjects of the studies. Lectins conjugated with fluorescein and ferritin are extensively used to investigate distribution and characteristics of surface-coating substances on spermatozoon and egg, which might play important roles in the processes of sperm capacitation, sperm/egg union, species-specificity of fertilization and block to polyspermy.