We conducted a retrospective study of symptom assessment calls for adult patients at a US call centre, Ask Mayo Clinic. A total of 27,979 symptom assessment calls were received from July 2006 to June 2007. Calls concerning female patients predominated in all age groups and accounted for 71% of calls, but decreased significantly with increasing age. The average duration of an adult call was 10 min, and the duration increased with increasing age of the adult patient. The greatest frequency (8%) of calls were related to symptoms of abdominal pain, followed in frequency by skin problems (6%), pregnancy-related issues (6%), cold symptoms (4%), and chest pain or chest discomfort (4%). Surrogate calls accounted for 14% of adult calls but the proportion was significantly higher (40%) if the patient's age was 80 years or greater. Call centres should recognize the sex- and age-related trends in calls and adjust the training of their registered nurses accordingly.