BACKGROUND Bisphenol A (BPA) and its analogue bisphenol S (BPS), widely utilized in numerous fields of industry, may seep into the environment and into human organisms. Hitherto, BPA was regarded as the bisphenol to which people were exposed to the greatest extent. As endocrine disruptors, bisphenols have negative effects on human health. Therefore, defining the levels of human exposure to these compounds is a key issue in toxicology. Hair analysis has been increasingly used for biomonitoring of bisphenols in humans, but information about the coexistence of BPA and BPS in human hair is extremely scarce. The present study aimed to analyze hair samples from 25 individuals from Olsztyn, northeastern Poland, to evaluate the levels of these 2 industrial pollutants. MATERIAL AND METHODS The method used in the research was liquid chromatography with a mass spectrometry technique. RESULTS BPA was found in 72% of samples analyzed and its concentration levels fluctuated from 3.6 to 52.9 ng/g (median 17.7 ng/g). The BPS concentration levels were higher - from 13.4 to 1054.9 ng/g (median 98.7 ng/g). We also found that gender, age, and the presence of artificial hair color (hair dye) did not affect the BPA and BPS levels in the hair. CONCLUSIONS This study has shown that hair samples may be used to measure the levels of bisphenols, and that exposure to BPS may be greater than that to BPA in this area. The investigation also revealed that hair analysis is a useful approach for the biomonitoring of BPA and BPS levels in human organisms.