We studied a web-based triage system which was accessible to the general public in the Netherlands. In a retrospective analysis we investigated the type of complaints that were submitted and the kind of advice provided. Over a period of 15 months, 13,133 different people began using the web-based triage system and 3812 patients went right through the triage process to the end. The most frequent complaints were common cold symptoms, such as cough and a sore throat (22%), itch problems (13%), urinary complaints (12%), diarrhoea (10%), headache (8%) and lower back pain (8%). Most commonly, the system generated the advice to contact a doctor (85%) and in 15% of the cases the system provided fully automated, problem-tailored, self-care advice. A total of 192 patients participated in a prospective study and completed an online survey immediately after the delivery of advice. A follow-up questionnaire on actual compliance was completed by 35 patients. Among these, 20 (57%) had actually complied with the advice provided by the system. A regression analysis revealed that intention to comply was strongly related to actual compliance. In turn, intention to comply was strongly related to attitude towards the advice (P < 0.001). Web-based triage can contribute to a more efficient primary care system, because it facilitates the gatekeeper function.