Telephone assessment of patients' symptoms is a widespread and useful means of triage, but patient safety could be compromised if patients are incorrectly determined to have non-urgent complaints and are not appropriately referred for urgent clinical evaluation. The limited prior research in this area indicated that potential for such under-referral exists. Conducted at a tertiary care pediatric hospital, this cohort study matched calls to the call center with admissions records to determine the proportion of calls that were not appropriately referred for evaluation. More than 5% of calls were under-referred, frequently associated with common diagnoses such as gastroenteritis and bronchiolitis. The study authors advocate for using the under-referral rate as a measure of call center quality of care. A previous WebM&M commentary highlights safety tips for telephone triage.