The androgen receptor (AR) is essential for prostate development and function, and its activity is crucial in prostate cancer progression. AR remains expressed throughout prostate cancer progression, and most hormone-refractory prostate cancers express AR. Mutations in AR, especially those that relax ligand specificity, may contribute to cancer progression and resistance to endocrine therapy by allowing AR activation by antiandrogens or other hormones. Alterations in AR coregulators and signal transduction pathways also modulate AR activity, influencing prostate cancer progression. AR trinucleotide repeats (CAG and GGN) affect AR function and may contribute to prostate cancer risk. AR amplification is more common in hormone-refractory prostate cancers and may enhance AR activity in low-androgen environments. Overexpression of AR coregulators, such as SRC-1, TIF-2, and SRC-3, is associated with increased prostate cancer progression and PSA levels. AR interacts with tumor suppressor genes like Rb, BRCA1, and PTEN, which regulate cell cycle progression and apoptosis. Loss of Rb expression is linked to increased prostate cancer progression, while PTEN inhibits AR function by degrading AR. These findings highlight the complex role of AR in prostate cancer development and progression, emphasizing the importance of AR activity and its regulation in therapeutic strategies.The androgen receptor (AR) is essential for prostate development and function, and its activity is crucial in prostate cancer progression. AR remains expressed throughout prostate cancer progression, and most hormone-refractory prostate cancers express AR. Mutations in AR, especially those that relax ligand specificity, may contribute to cancer progression and resistance to endocrine therapy by allowing AR activation by antiandrogens or other hormones. Alterations in AR coregulators and signal transduction pathways also modulate AR activity, influencing prostate cancer progression. AR trinucleotide repeats (CAG and GGN) affect AR function and may contribute to prostate cancer risk. AR amplification is more common in hormone-refractory prostate cancers and may enhance AR activity in low-androgen environments. Overexpression of AR coregulators, such as SRC-1, TIF-2, and SRC-3, is associated with increased prostate cancer progression and PSA levels. AR interacts with tumor suppressor genes like Rb, BRCA1, and PTEN, which regulate cell cycle progression and apoptosis. Loss of Rb expression is linked to increased prostate cancer progression, while PTEN inhibits AR function by degrading AR. These findings highlight the complex role of AR in prostate cancer development and progression, emphasizing the importance of AR activity and its regulation in therapeutic strategies.