Background: The purpose of this study is to determine the incidence of electrolyte and ABG abnormalities in infants with HPS and also we evaluate other parameters of the study. ‎

Materials and Methods: This descriptive study covers 161 infants with HPS hospitalized in children Medical center of Tehran university underwent surgical repair from march 1996 to march 2002 . ‎

Results & Conclusion: The results indicated that Hypokalemic metabolic alkalosis had occurred in 40% of patients. ‎The sex ratio was 3/1 =M/F and the most time of presentation was between 15t and 5st week and the most presenting sign was vomiting. Clinical icter happened to be found in 15% of patients. The incidence of accompanying anomalies was 9% and olive sign was palpable in 40%. ‎The best way for evaluating and diagnosis was sonography. ‎The mean period to begin postoperative feeding was 30 hours' no complication related to option was reported after operation.