A close relationship exists between prostate volume and prostate-specific antigen (PSA). Clinical decisions must be determined based on the variability of PSA. Screening with the PSA assay has contributed to early detection of prostate cancer. Some important undetermined issues are the optimal cutoff values of PSA, the proportion of free to total PSA, and the clinical usefulness of complexed PSA. Current articles demonstrating novel markers (human kallikrein-2, BPSA, and pro PSA) and artificial neural networks are introduced.