This study was undertaken to determine the accuracy of sonographic examination in the prenatal diagnosis of neural tube defects. The study population consisted of 237 patients divided into three groups according to the indication for the sonographic examination. The overall sensitivity of sonography in the diagnosis of neural tube defects was 94.7%, and the specificity was 98.3%. A false positive diagnosis of spina bifida occurred in a fetus affected with ventriculomegaly, omphalocele, severe kyphosis and scoliosis. There were three false negative diagnoses of spina bifida.