This study suggests that when screening the general population for prostate cancer, MRI using a score of 4 or 5 to define a positive test result, compared with PSA testing alone at a level of 3 ng/mL or higher, might lead to more men being diagnosed with clinically significant cancer, without increasing the number of men advised to undergo biopsy or overdiagnosed with clinically insignificant cancer. The gene discussed is KLK3; the disease is prostate carcinoma.