ObjectivesIdentify the sources of overuse from the point of view of the Spanish primary care professionals, and analyse the frequency of overuse due to pressure from patients in addition to the responses when professionals face these demands.DesignA cross-sectional study.SettingPrimary care in Spain.ParticipantsA non-randomised sample of 2201 providers (general practitioners, paediatricians and nurses) was recruited during the survey.Primary and secondary outcome measuresThe frequency, causes and responsibility for overuse, the frequency that patients demand unnecessary tests or procedures, the profile of the most demanding patients, and arguments for dissuading the patient.ResultsIn all, 936 general practitioners, 682 paediatricians and 286 nurses replied (response rate 18.6%). Patient requests (67%) and defensive medicine (40%) were the most cited causes of overuse. Five hundred and twenty-two (27%) received requests from their patients almost every day for unnecessary tests or procedures, and 132 (7%) recognised granting the requests. The lack of time in consultation, and information about new medical advances and treatments that patients could find on printed and digital media, contributed to the professional’s inability to adequately counter this pressure by patients. Clinical safety (49.9%) and evidence (39.4%) were the arguments that dissuaded patients from their requests the most. Cost savings was not a convincing argument (6.8%), above all for paediatricians (4.3%). General practitioners resisted more pressure from their patients (x2=88.8, P<0.001, percentage difference (PD)=17.0), while nurses admitted to carrying out more unnecessary procedures (x2=175.7, P<0.001, PD=12.3).ConclusionSatisfying the patient and patient uncertainty about what should be done and defensive medicine practices explains some of the frequent causes of overuse. Safety arguments are useful to dissuade patients from their requests.