Abstract: 　Objective　To determine whether pyloric measurements with ultrasound, that muscle thickness and channel of pyloric, correlated with weight and age in patients with hypertrophic pyloric stenosis (HPS). Methods A retrospective analysis was conducted on 111 cases diagnosed with HPS by operation from 2008 to 2012. Pearson correlation and linear regression analyses were used to determine if there were sta¬tistically significant associations between these combinations of factors: age and pyloric muscle thickness, weight and pyloric muscle thickness, age and pyloric length, and weight and pyloric length. Results Patients’mean age was 39.1 d (8-92 days). Their mean weight was 4.3 kg (2.2-7.9 kg). Mean pyloric muscle thickness was 4.8 mm (2-4.6 mm), and mean pyloric length was 17.5 mm (12-23.5 mm). Pearson correlation coefficient analysis showed a significant correlation between age and muscle thickness (r=0.6, P<0.001) as well as weight and muscle thickness (r=0.486, P<0.001). No significant correlation was found be¬tween pyloric length and age or weight. Linear regression analysis demonstrated similar results. Conclusions In patients with HPS, pyloric muscle thickness was directly related to age and weight. Smaller and younger infants with suspected diagnosis of HPS should be followed up even though the minimum diagnostic criterion for muscle thickness or length was not found on ultrasound.