Within the framework of the National Research and Development Program No. 1/016 /2001 the authors determined the population levels of ionizing and nonionizing radiations, elaborated the system of assays for detection of biological effects including dose-effect relationships, studied the roles of protective and sensitizing factors in the effect modification. The radium content of building materials were determined as well as the indoor radon activity concentrations and the magnetic induction fields around household equipment operating with 50 Hz. Biological dosimetry techniques were categorized according to the indication time. In addition, radiation sensitivity of intracellular antioxidant enzymes and the antioxidant capacity of blood sera were measured.