Benign prostatic hyperplasia (BPH) is a kind of common noncancerous prostate gland enlargement with growing tendency in recent years. 5α-reductase is the key enzyme responsible for dihydrotestosterone biosynthesis and has been considered as an important target for designing inhibitors as potent therapeutic agents for BPH. Finasteride, the first steroidal 5α-reductase inhibitor, has been marketed worldwide as a drug for BPH. During these years, many other novel types of 5α-reductase inhibitors are being studied. This review summarizes recent advancement in steroidal 5α-reductase inhibitors.