Background: Immunoassay is an appropriate method for measuring hormones and other protein compounds like a prostate-specific antigen (PSA). This antigen is a tumor marker of prostate cancer which can be identified by screening. Among the numerous available solid phases a coated tube is the most popular one. Material and methods: We have used a monoclonal antibody (mAb) against the PSA. One of the pairs of monoclonal antibodies has been used for preparing the PSA tracer by labeling to radioactive iodine (125I) and the other one – for the coating of polystyrene tubes. In the solid phase method we have used the adsorption technique for coating the monoclonal antibody in polystyrene tubes. We have used adsorption as a mode of coating and plastic tubes as a solid phase. The reaction takes place between the antigen molecule in the patient serum and the two antibodies (anti-PSA mAb) in the tracer and coated tubes, and hence these assays are called solid phase assays. The determination of PSA is based on the immunoradiometric assay (IRMA). The samples or standards are incubated in monoclonal antibody-coated tubes with the second 125I-labelled antibody. After the incubation period (two hours) the liquid contents of the tubes are aspirated and washed. Results: After running the assay the results have showed a correlation between the concentrations of the serum PSA tested by the locally made coated tubes and the commercial ones. So, we can use the locally made reagents to measure the PSA not only for the laboratories performing a large number of tests, but also for the whole country in screening the prostate cancer which will surely be a cost-effective project. Finally, as the method is isotopic, it is more robust compared to the non-isotopic markers and presents a true immunoassay. Conclusions: Many solid phases have specific reactive groups which can be activated by a variety of biochemical methods. This research shows that we can manufacture the cost-effective IRMA kits by producing locally the antibody-coated tubes for PSA. And they can be used in mass screening of the prostate cancer for men over 50 in any country. Finally the same protocol for coating monoclonal antibodies can be used for other tumor markers like CEA, CA15-3 and AFP if we have their specific monoclonal antibodies.