Objectives: This study was designed to identify factors that influenced the degree of enhancement of prostate cancer on contrast-enhanced transrectal ultrasonography (CETRUS). Methods: 139 patients suspected of prostate cancer were evaluated with CETRUS followed by systematic and targeted transrectal ultrasound-guided biopsies. The degree of enhancement of the lesions was objectively measured using peak intensity with time-intensity curve analysis software. Ultrasound findings were correlated with clinical characteristics as well as biopsy and radical prostatectomy findings. Results: Prostate cancers were detected in 230 biopsy sites from 91 patients. The mean peak intensity value of prostate cancer was significantly higher than that of the benign lesions (9.82¡3.73 vs 7.51¡2.97; p,0.001), and the peak intensity value of the cancer foci varied across the prostate. The mixed model analysis revealed that the location and Gleason score of tumour foci were the influencing factors of the peak intensity value, and the former had a stronger influence upon peak intensity than the latter (p50.000 and 0.040, respectively). However, age, prostate volume or serum prostate-specific antigen of the patient had no significant influence on the peak intensity value (p.0.05). Furthermore, the peak intensity value of tumours larger than 5 mm diameter was significantly higher than tumours of 5 mm or smaller diameter (9.28¡2.46 vs 6.69¡2.65; p,0.001). Conclusions: The prostate cancer lesions with a higher Gleason score and larger tumour size which were located in the lateral peripheral zone (PZ) were more likely to show a marked enhancement. Lesions with lower peak intensity that are located in the medial PZ should also be treated as suspicious. Prostate cancer is the most commonly diagnosed cancer in males, accounting for 28% of new cancer diagnoses in males and 11% of cancer-related deaths, with an expected 32 050 prostate cancer-specific mortalities in 2010 [1]. The imaging of prostate cancer is central to early detection and staging. However, it is generally acknowledged that detection and localisation of prostate tumours using greyscale ultrasound is poor, because suspicious hypoechoic areas represent cancer in only 9-53% of cases [2][3]. Furthermore, up to 30% of prostate cancers are isoechoic [4][5]. Conventional prostate ultrasound has little advantage over digital rectal examination for detecting malignant areas. Consequently, new strategies for prostate cancer detection are required. Contrast-enhanced ultrasound (CEUS) is a real-time imaging technique with the capability of visualising perfusion patterns [6][7][8]. This imaging technology has revealed promising perspectives in the diagnosis of prostate cancer owing to its ability to improve the visualisation of tumour vascularity. Several studies have reported that CEUS-targeted biopsy detected more cancer than systematic biopsy by identifying the area with greatest enhancement of the prostate [9][10][11][12]. In a recent study reported by Tang et al [13], the haemodynamic ...