Prostate cancer (PCa) is the most common cancer in men in many industrialised countries and causes substantial mortality.1 Screening based on blood prostate-specific antigen (PSA) has been shown to decrease PCa mortality, but the evidence from randomised trials is not conclusive.2 3 Systematic reviews of randomised controlled trials have concluded that PSA screening may at best lower PCa mortality, but not all-cause mortality. Here, KLK3 is linked to prostate cancer.