The aim of the present study was to find out whether Ganoderma lucidum (GL) can be used as a clinically effective medicine for the management of prostatic hyperplasia. In vitro studies were conducted to assess the 5α-reductase inhibitory potential of GL. A biochemical marker viz. β-sitosterol was identified and characterised in the extracts utilising high-performance thin-layer chromatography. Testosterone (3 mg kg(-1) s.c.) was administered to the rats along with the test extracts (10, 20 and 50 mg kg(-1) p.o.) and β-sitosterol (10 and 20 mg kg(-1) p.o.) for a period of 28 days. Finasteride was used as a positive control (1 mg kg(-1) p.o.). GL extracts attenuated the increase in the prostate/body weight ratio induced by testosterone. Petroleum ether extract exhibiting the best activity. Ethanolic extract also exhibited significant activity. The urine output also improved significantly, which emphasise the clinical implications of the study. Testosterone levels measured weekly and prostate-specific antigen (PSA) levels measured at the end of the study also support our claims. The PSA levels decreased in the extract-treated groups, indicating their usefulness in the treatment of benign prostatic hyperplasia. Histological studies have shown a considerable improvement in the prostatic histoarchitecture in the extract-treated groups when compared to the testosterone-treated group.