In this longitudinal study, fetal bipariétal diameters (BPD), femur length (FL), abdominal circumference (AC), head circumference (HC), mean head diameters (MHD), mean abdominal diameters (MAD), humerus length (HL), and biocular diameters (BOD) were measured ultrasonographically between 14-41 weeks' gestation in 30 normal fetuses. By using multiple regression analyses, gestational age prediction curves were constructed for each parameter and evaluated in regard to other data. The comparison of our gestational age curves for BPD, AC, and HC were in good agreement with the results presented by Hadlock et al, and for FL, HL and BOD with Jeanty et al. The differences between our values and the data for MHD and MAD were great especially in the third trimester, approaching 2.6 weeks on the average. These differences in the tables may result from different population studies, genetic variations or from technical errors. It is concluded that, for the establishment of gestational age, new nomograms should be constructed for each fetal parameter, considering the differences presented in this preliminary study.