Background Early feeding after pyloromyotomy for hypertrophic pyloric stenosis (HPS) has been advocated because this would lead to earlier discharge. However, some authors remain reluctant to introduce early feeding because of concern about postoperative vomiting. This study aimed to clarify the effects of early versus later feeding after laparoscopic pyloromyotomy on postoperative vomiting, time required to reach full oral feeding, hospital stay, and follow-up evaluation. Methods During the period from October 1993 through March 2002, 185 infants underwent laparoscopic pyloromyotomy for HPS. Of these patients, 164 patients were included in the study. The initial feeding was within 4 h after surgery in group A and after 4 hours in group B. The outcome variables were postoperative vomiting subdivided into vomiting requiring adjustment of the feeding schedule or not, time required to reach full feeding, hospital stay, and vomiting as well as weight gain at follow-up assessment. Results In 23% of the 62 patients of group A and in 6% of the 102 patients of group B ( p = 0.003), vomiting was so severe that it necessitated modification of the feeding schedule. Th time required to reach full feeding and the postoperative hospital stay were similar in the two groups. Analysis of the subgroups that required modification of the feeding schedule because of vomiting showed a significant delay in time required to reach full feedings as well as a significant delay in hospital discharge. There was an 11% incidence of ongoing vomiting after discharge irrespective of early or later feeding. Weight gain at follow-up assessment did not differ significantly between the two groups, and did not bear any relations to in-hospital vomiting. Conclusions Feeding within 4 h postoperatively leads to more severe vomiting than later feeding. Vomiting leads to discomfort for the child, anxiety for the parents, a prolonged time required to achieve full oral feeding, and a prolonged postoperative hospital stay. However, clinical outcome after discharge is not adversely affected by early feeding. According to this study, it appears that it would be better to withhold feeding for the first 4 h after surgery.