The records of off-hours calls received by the University of Colorado Pediatric Group Practice from 4:30 p.m. throughout 8:00 a.m. weekdays and all day Saturday, Sunday, and holidays were audited. An answering service and pageboy system ensured 24-hour, 7-day-a-week accessibility through a single telephone number. The four practices received 2386 after-hours calls from November 1978 to October 1980. An average of 104 calls per month were received with approximately four calls per day on weekday evenings and six calls per day on Saturday, Sunday, and holidays. Five concerns accounted for 49 percent of all after hours calls: fever, vomiting and/or diarrhea, upper respiratory infection (URI), earache, and rash. While 75 percent of families made fewer than four calls per year, 4 percent made at least 12 calls per year, accounting for 18 percent of all calls. Families calling three or more times a month were defined as "frequent users" and accounted for 22 percent of a given month's calls. Most calls from the same families (55%) occurred within a 24-hour period and dealt chiefly with parental concerns about fever, vomiting and diarrhea, URIs, ear infection, accident, and rashes. The additional responsibility that residents assume in taking calls for the Pediatric Group Practice while on other off-hour assignments was not excessively demanding, and cost of the answering service was easily absorbed by group practice revenues.