Ultrasound measurement of fetal body dimensions provides a non-invasive and precise way of obtaining information of fetal size. We applied clinically two methods for fetal weight estimation described by Hansmann. The first method employed ultrasonic measurement of the fetal biparietal diameter (BPD) and the transverse diameter through the lower fetal thorax aperture (THQ). This method was applied to 383 fetuses within 4 days of delivery. Weight range of the birth weights was 680-5070 g. SD of prediction errors was 264 g. The method overestimated (p <0.01) the fetuses weighing less than 3000 g and underestimated (p <0.001) the fetuses weighing above 4000 g. The results for the fetuses weighing between 3000 and 4000 g were adequate. The second method employed the BPD, THQ and the gestational age for fetal weight prediction. We applied this method to 174 fetuses and obtained SD of prediction errors of 259 g. The results were adequate in all weight groups except for the fetuses weighing over 4000 g; this group was underestimated (p <0.001). The reason for the inaccuracy in the high weight groups is discussed. It is concluded that both formulas for fetal weight prediction can be used clinically when the fetal weight is expected to be below 4000 g.