In this communication a limited analytical study is described on the new Prostatus PSA Free/Total assay. The study is considered as a side study of the European Randomized Study of Screening for Prostate Cancer. The between-day imprecision with 8 control samples for free prostate-specific antigen ranged from 10.3% at 0.17 microg/l to 3.7% at a concentration of 35.5 microg/l, while for total prostate-specific antigen we found 7.3% at 0.69 microg/l and 4.3% at 70.7 microg/l. For total prostate-specific antigen we found excellent agreement between the new assay and well-established assays like Abbott IMx and Hybritech Tandem-E, both for prostate cancer and benign prostate hyperplasia specimens. The age-specific reference ranges proved to be well-comparable with the literature data both for free and total prostate-specific antigen.