Importance: Analyses of volume-outcome relationships in adult surgery have found that hospital and physician characteristics affect patient outcomes, such as length of stay, hospital charges, complications, and mortality. Similar investigations in children's surgical specialties are fewer in number, and their conclusions are less clear.Objective: To review the evidence regarding surgeon or hospital experience and their influence on outcomes in children's surgery.Evidence Review: A MEDLINE and EMBASE search was conducted for English-language studies published from January 1, 1980, through April 13, 2012. Titles and abstracts were screened in a standardized manner by 2 reviewers. Studies selected for inclusion had to use a measure of hospital or surgeon experience as a predictor variable and had to report postoperative outcomes as dependent response variables. Included studies were reviewed with regard to methodologic quality, and study results were extracted.Findings: Sixty-three studies were reviewed. Significant heterogeneity was detected in exposure definitions, outcome measures, and risk adjustment, with the greatest heterogeneity seen in appendectomy studies. Various exposure levels were examined: hospital level in 48 (68%) studies, surgeon level in 11 (17%), and both in 9 (14%). Nineteen percent of studies did not adjust for confounding, and 57% did not adjust for sample clustering. The most consistent methods and reproducible results were seen in the pediatric cardiac surgical literature. Forty-nine studies (78%) showed positive correlation between experience and most primary outcomes, but differences in outcomes and exposure definitions made comparisons between studies difficult. In general, hospital-level factors tended to correlate with outcomes for high-complexity procedures, whereas surgeon-level factors tended to correlate with outcomes for more common procedures.Conclusions and Relevance: Data on experiencerelated outcomes in children's surgery are limited in number and vary widely in methodologic quality. Future studies should seek both to standardize definitions, making results more applicable, and to differentiate procedures affected by surgeon experience from those more affected by hospital resources and system-level variables.