Patients can only make well-informed decisions if the information they are given by health professionals is based on scientific evidence. In this study, we assessed the foundation in evidence of free, publicly available telephone consultations in Germany.From March 2013 to January 2014, four hidden clients seeking information asked standardized questions about three medical topics (screening for colorectal cancer, for glaucoma, and for trisomy 21) and three dental ones (the sealing of dental fissures, professional dental cleaning, and mercury detoxification). Depending on the topic, the questions addressed such issues as the risk of disease and the purpose, content, validity, benefits, and risks of potential diagnostic and therapeutic measures. All identifiable telephone consultation services that provided counselling on the above topics were included in the study (23 government-sponsored institutions, 31 institutions independently run by physicians, 521 institutions under religious auspices, 25 dental counselling services).Of the 599 telephone consultation services that were identified, 567 were contacted; 404 did not offer any relevant counselling. A total of 293 conversations were held with the remaining 163 consultation services. Six of these conversations fully met predefined criteria for evidence-based counselling. The percentage of appropriate answers to the key questions on each topic was 5% for colorectal cancer screening (7/140), 23.8% for glaucoma screening (25/105), 33.9% for trisomy 21 screening (121/357), 27.5% for the sealing of dental fissures (28/102), 16.2% for professional dental cleaning (19/117), and 12.9% for mercury detoxification (12/93). The percentage of appropriate answers also varied depending on the type of institution: 26.8% for government-sponsored institutions (67/250), 4.5% for institutions independently run by physicians (4/88), and 31.1% for institutions under religious auspices (82/264).The medical and dental counselling now offered over the telephone by the types of institutions included in this study does not satisfy the criteria for evidence-based health information.