The aim of this paper was to review the effects of some important substances involved in the induction of sperm plasma membrane changes referred to as acrosome reaction, namely cholesterol (C), calcium (Ca(2+)) and progesterone (P(4)). For this purpose, mechanisms of capacitation and acrosome reaction (AR) as well as the processes, C, Ca(2+) and P(4) are involved in, are described. Subsequently, to get a better insight into possible beneficial and detrimental effects on sperm function, the occurrence of these molecules in semen extenders is discussed.