The authors describe the approaches to obtaining specific antibodies to placental lactogen (PL) with required analytical parameters in order to investigate this hormone by RIA. A study was made of the dependence of the analytical parameters of antibodies on a dose of immunogen, the type of adjuvant (Freund's adjuvant, pertussoid monovaccine), a scheme of immunization, etc. The authors proposed that specific (primary) antibodies immobilized on the staphylococcal reagent A protein should be used as fixing and separating agents in the radioimmunoassay test-system for the determination of PL concentration in order to improve the parameters of the analytical system and to reduce the time and procedure of analysis. The RIA determination of the PL serum concentration was used for the production of kits of reagents RIO-PL-125I.