Infradian rhythms of sex hormones in women are important in several physiological and pathophysiological processes. Detailed analyses of these rhythms are difficult due to problems with sampling. Salivary levels of sex steroids are widely used when repeated sampling is needed. However, a description of variation during the menstrual cycle with daily sampling is lacking. In our study salivary levels of testosterone, estradiol and progesterone were measured in samples collected daily by 17 young healthy women (21,2+/-0,7 years) during one menstrual cycle. Sex steroid levels were determined using radioimmunoassay. The dynamics of salivary sex steroids in our study resembles the known dynamics in plasma. Similar patterns for estradiol and testosterone confirm the hypothesis that in women testosterone serves as a precursor for estradiol. The primary (periovulatory) peak and secondary (luteal) peak of testosterone are followed by similar peaks of estradiol. Progesterone reaches maximum concentrations during the luteal phase. This study shows that analysis of salivary levels of sex steroids are informative and can be used in neuroendocrine, chronobiological and other research areas, when repeated sampling is needed.