Total estrogens, estradiol and estriol were determined by radioimmunoassay in the blood of 141 pregnant women during their 26th and 31st weeks of pregnancy, and the results were correlated with dietary patterns and nutrient intakes during pregnancy, assessed through a semiquantitative food frequency questionnaire. No food group or nutrient showed a significant (p less than 0.05) association with any of the examined hormones at both the 26th and the 31st week of pregnancy. Relatively more consistent were a positive association between consumption of starchy roots (potatoes) and all the indicated hormones, and a negative association between vitamin A and estradiol and total estrogens; however, the multitude of comparisons hinders a biologic interpretation at this time. There was suggestive evidence that weight gain up to the 31st week of pregnancy was positively associated with both total estrogens (p = 0.09) and estradiol (p = 0.11). The present study has limitations reflecting the relatively small sample size and the problems inherent in epidemiologic methods assessing nutritional intakes. However, the findings suggest that quantitative aspects of diet, as reflected in pregnancy weight gain, may be more important than dietary composition in influencing levels of pregnancy estrogens and in affecting the occurrence of gonadal germ cell tumors and other conditions that may be associated with them.