The European Randomized Study of Screening for Prostate Cancer (ERSPC) has shown a 21% reduction in prostate cancer mortality by PSA-based screening. The aim of the study is to evaluate screening effect on prostate cancer incidence and mortality in relation to number of screening rounds attended.Experimental Design: The participants in the screening arm of the Finnish trial (31,867 men) were classified according to screening attendance in a time-dependent fashion. Initially, all men in the screening arm were regarded as nonattenders until the first screening attendance, then remained among the once-screened until the second screen and similarly for the possible third round. The control arm was the reference. Follow-up started at randomization and ended at death, emigration, or end of 2013. Prostate cancer incidence and mortality, as well lung cancer and overall mortality were evaluated.