Abstract Background Telephone consultations in general practice are on the increase. However, data on their efficiency in terms of out-of-hours general practitioner (GP) workload, visits to hospital emergency departments (ED), cost, patient safety and satisfaction are relatively scant. The aim of this trial is to assess the effectiveness of telephone consultations provided by French emergency call centres in patients presenting with isolated fever or symptoms of gastroenteritis, mainly encountered diseases. Methods/design This is a prospective, open-label, multicentre, pragmatic, cluster randomised clinical trial of an estimated 2880 patients making an out-of-hours call to one of six French emergency call centres for assistance with either fever or symptoms of gastroenteritis without seriousness criteria. Each call is handled by a call centre physician. Out-of-hours is 8 p.m. to 7.59 a.m. on weekdays, 1 p.m. to 7.59 a.m. on Saturdays and round-the-clock on Sundays and school holidays. Patients will be enrolled over 1 year. In the intervention arm, a telephone consultation based on a protocol, the formal Telephone Medical Advice (fTMA), is offered to each patient calling. This protocol aims to overcome a physical consultation during out-of-hours periods. It offers reassurance and explanations, advice on therapeutic management which may include, in addition to hygiene and diet measures, a telephone prescription of antipyretic, analgesic, rehydration medication or others, and recommendations on surveillance of the patient and any action to be taken. The patient is invited to call again if the condition worsens or new symptoms develop and to make an appointment with their family GP during office hours. In the control arm, the call centre physician handles calls as usual. This physician can carry out a telephone consultation with or without a telephone prescription, dispatch an on-duty GP, the fire brigade or an ambulance to the patient, or refer the patient to an on-duty physician or to the ED. Each patient will receive a follow-up .