Background: Although the PSA test has been used in Korea for over 20 years, the incidence of prostate cancer has risen, and the associated mortality has increased about 13-fold over the 20-year period. Also, several investigators have suggested that Asians in America are more likely to present with more advanced prostate cancer than Caucasians. We compared the characteristics of native Koreans and Americans (Caucasians and African-Americans) undergoing radical prostatectomies in Korea and the US. Materials and Methods: Study subjects comprised patients at Korean and US hospitals from 2004 to 2012 who had undergone radical prostatectomies. We compared the characteristics of the subjects, including age, preoperative prostate-specific antigen (PSA) levels, body mass index (BMI), Gleason score, and pathological T stage. Results: In total, 1,159 males (502 Koreans, 657 Americans) were included. The Korean and American patients had mean ages of $67.1{pm}6.6$ and $59.2{pm}6.7$ years, respectively. The mean preoperative PSAs were $15.4{pm}17.9$ and $6.2{pm}4.6ng/mL$ (p=0.0001) and the mean BMIs were $23.6{pm}2.6$ and $28.7{pm}4.4kg/m^2$ (p=0.0001), respectively. Pathological localized prostate cancer represented 71.7% of cases for Koreans and 77.6% for Americans (p=0.07). According to age, Koreans had higher T stages than Americans in their 50s (p=0.021) and higher Gleason scores than Americans in all age groups. According to PSA, Koreans had higher Gleason scores than Americans for PSA >10 ng/mL (p<0.05). According to prostate size and Gleason scores, Koreans had higher PSA values than Americans (p<0.01). Conclusions: These results show that Korean patients have elevated risk of malignant prostate cancers, as indicated by the significantly higher Gleason scores and PSAs, suggesting a need for novel prostate cancer treatment strategies in Korea.