Tumour hyperthermia, although potentially a powerful therapeutic agent and radiation sensitizer, is hindered by a number of considerations including inhomogeneous heating of deep seated tumours due to energy deposition and perfusion issues. One solution is to design hyperthermia sensitizers to amplify the effects of hyperthermia, particularly at cold spots within the tumour undergoing treatment. This study examined the use of Quercetin, a flavonoid drug shown previously to antagonize the expression of HSP72 and induce apoptosis as a sensitizer of prostate cancer growth in vivo. Quercetin dose-dependently suppressed PC-3 tumour growth in vitro and in vivo. When combined in a treatment protocol with hyperthermia, quercetin drastically inhibited tumour growth and potently amplified the effects of hyperthermia on two prostate tumour types, PC-3 and DU-145 in vivo. These experiments, thus, suggest the use of Quercetin as a hyperthermia sensitizer in the treatment of prostate carcinoma.