OBJECTIVE In this study, morphometric developments of the sphincter of Oddi in human fetuses were observed. METHODS We observed 113 human fetuses consisting of 67 male and 46 female subjects, whose ages varied between 14 to 40 weeks who showed no signs of any pathology or anomaly externally. The common external measurements of fetuses were carried out, followed by abdominal dissection to determine where the sphincters of Oddi were localized within the duodenum and pancreas. Histological specimens of tissue samples were gathered from the inner wall of the duodenum where it was assumed that the sphincters of Oddi had been localized. The parameters of total external diameters, lumen diameters, wall thickness, diameters of ductus choledochus and ductus pancreaticus, and the distance between these two structures, which are also known as the origins of the sphincter of Oddi, were measured by using a light microscope. The standard deviations of the measurements were calculated for each gestational week and trimester. RESULTS The calculations suggested that there were statistically significant correlations between gestational age and all of the other parameters with the exception of the ductus choledochus (p<0.001). It was observed that the wall thickness of the ductus choledochus increased at the first half of the fetal stage and decreased at the second half, as the lumen diameter increased through the 40th week. The gender difference was not statistically significant (p>0.05). CONCLUSIONS The data we collected in our study were considered as useful for the evaluation of the development of the sphincter of Oddi area and fetal stage.