SRY is the only gene currently known to be involved in the process of sex determination. A number of cloned genes probably participate in gonadal development: the MIS (also called AMH), the SOX9, the SF1, the DAX1, the WT1 and the DSS etc. Some gene model for mammalian sex determination such as Z-gene model and DSS-gene model etc. have recently been proposed. Those models provide a rational explanation not only for the cases of XX and XY sex reversal currently known to occur in humans and other mammals,but also for molecular mechanism of sex determination. Many questions of mammalian sex determination still remain unresolved. The identification and functional analysis of other genes in the mammalian sex determining cascade will determine the validity of this hypothesis.