Patients admitted on the weekend may have higher rates of complications and mortality. Known as the weekend effect, this phenomenon has been demonstrated for a diverse range of diagnoses, including myocardial infarction and traumatic brain injury. This analysis of more than 400,000 pediatric surgical admissions also found evidence of a weekend effect, as patients who underwent a weekend surgical procedure had higher rates of mortality and postoperative complications. Although the absolute increase in mortality was small, the proportional increase was similar to prior studies. A persistent question regarding the weekend effect is whether higher weekend mortality reflects patient characteristics (i.e., patients admitted on the weekend are more severely ill) or health system characteristics (i.e., decreased availability of clinical services on the weekend). An Australian study that attempted to answer this question found a mixed picture, with certain diagnoses (especially those requiring urgent admission and treatment) appearing to have increased mortality for weekend admissions due principally to health system factors.