Objectives Since for the sales of over-the-counter (OTC) medicines, prescribing physicians are not involved, and written instructions on/in the medicine boxes are inefficient, druggists and pharmacists are important gatekeepers in preventing customers’ accidents. In this study we investigated the sales routines, and compliance with sales protocols, in order to evaluate that gatekeeper's function. Methods By means of the mystery shopping method, 228 pharmacies and drugstores in The Netherlands were visited and a naproxen 275 mg medium-risk medicine was requested for a (fictitious) patient who was suffering from severe back pains. According to the sales protocols the vendors should never sell the requested medicine, because the mystery shoppers only gave an answer to one of the four mandatory sales protocol questions. Furthermore, the requested medicine is not the right or best choice for back pains. Four different scenarios were used in a 2 × 2 design (8-year-old patient vs. 25-year-old patient, and 1 box with 12 pills vs. 3 boxes with 12 pills). Results Of the drugstores and pharmacies only 16.7% complied with the sales protocols and did not sell the specific (or comparable) medicine, after asking all four mandatory questions (or already after one, two or three questions). Most vendors (83.3%) did not comply and sold the requested medicine, a comparable medicine, or even a more risky medicine after no question at all (or after asking some or even all four questions). Although both score low, pharmacists show better compliance (23.9%) than druggists (10.1%). Conclusions When it comes to OTC medicines, druggists and pharmacists largely commit sloppy sales. The expected gatekeeping function of pharmacists and druggists is very limited, and customers might be in danger of inappropriate medicine selection, quantity and usage. We call for thorough evaluation of the over-the-counter system, improvement of the educational programs for medicine providers, and national campaigns to inform the public.