The steroidal enzyme cytochrome P450_17α catalyzes the conversion of progesterone and pregnenolone into androgens, androstenedione and dehydroepiandrosterone, respectively, the direct precursors of estrogens and testosterone.  Dihydrotestosterone is the principal active androgen in the prostate, testosterone is also an active stimulant of the growth of prostatic cancer tissue.  Inhibition of this enzyme as a mechanism for inhibiting androgen biosynthesis could be a worthwhile therapeutic strategy for the treatment of PCA.  In this paper, four categories of steroidal inhibitors of cytochrome P450_17α will be reviewed, a diverse range of steroidal inhibitors had been synthesized and shown to be potent inhibitors of P450_17α .