Twenty two young infants presenting with non-bilious vomiting were examined by ultraso-nography in order to evaluate the diagnostic value of ultrasonography in hypertrophic pyloric stenosis. We analysed the ultrasonographic findings in 16 cases of the hypertrophic pyloric stenosis which were compared with operative findings. Our results were as follows: 1.Hypertrophic pyloric stenosis were mostly diagnosed between 3 and 8 weeks of age and had high incidence in first male baby also pyloric mass were palpated in 80% of cases. Eight case who were diagnosed within 4 weeks of age had early onset of symptom with short duration many had no palpable mass. 2. All cases with hypertrophic pyloric stenosis the demomstrated the pyloric muscle thickness to be 4mm or greater the pyloric diameter to be 1.0cm or greater and the pyloric channel length to be 1.6cm or greater therefore when ultrasonographic measurements were com-patible with the above the definite diagnosis of hypertrophic pyloric stenosis could be made. 3. Operative measurement of the pyloric muscle thickness was between 4 and 7mm (mean 5.0mm) the pyloric diameter was 1.0 and 2.0 cm(mean 1.67cm) the pyloric channel length was between 2.0 and 3, 0cm(mean 2.24cm) showing good correlation with ultrasonographic measurements 4. Other findings on ultrasonography which could help diagnosis of hypertrophic pyloric stenosis included delayed gastric empting hyperperistalsis teat and beak sign failure of passage or little passage of fluid traget and doughnut sign cervix sign and double tract sign.5. Ultrasonography was useful in postoperative course and prognosis of hypertrophic pyloric stenosis and also differentiating other cause of non-bilious vomiting. In conclusion ultrasonograhy was a quick safe and accurate method of evaluating young infants with non-bilious vomiting and it should be the initial diagnostic procedure in infants suspected of hypertrophic pyloric stenosis because of early detect6ability high accuracy of pyloric measurememts and usefullness in postpyloromyotomy follow-up