This study was conducted to characterize Doppler blood flow signals in prostatic cancer using power Doppler imaging with a transrectal probe. Both the localization and vascularity of blood flow in the prostate were compared between patients with prostatic cancer and those with benign prostatic hyperplasia (BPH). The prominent accumulation of blood flow signals (hypervascular lesion) was recognized in all the cases with prostatic cancer, compared to only 2 (4%) of 47 with BPH (p < 0.001). Power Doppler imaging is promising for the detection of prostatic cancer.