The prostate-specific antigen (PSA) is secreted by all types of prostate epithelial cells and has been used as a biological marker for prostate diseases for three decades. Although PSA is one of the most useful tumour markers in oncology, its specificity is limited by confounding conditions, e.g. both BPH and prostatitis can also lead to elevated serum PSA levels. In the case of increased PSA values, it is recommendable to perform additional tests for exclusion of different prostate diseases. Despite the decreased PSA range, further long-term diagnostic monitoring of the prostate is advisable.