ObjectivesThe factors determining individuals’ self-reported behavioural responses to direct to consumer advertising of prescription drugs were explored with an emphasis on ‘at-risk’ individuals’ responses.DesignNationally representative cross-sectional survey.SettingCommunity living adults in New Zealand.Participants2057 adults (51% women).Primary outcome measuresSelf-reported behavioural responses to drug advertising (asking a physician for a prescription, asking a physician for more information about an illness, searching the internet for more information regarding an illness and asking a pharmacist for more information about a drug).MethodsMultivariate logistic regressions determined whether participants’ self-reported behavioural responses to drug advertising were predicted by attitudes towards advertising and drug advertising, judgements about safety and effectiveness of advertised drugs, self-reported health status, materialism, online search behaviour as well as demographic variables.ResultsIdentifying as Indian and to a less extent Chinese, Māori and ‘other’ ethnicities were the strongest predictors of one or more self-reported responses (ORs 1.76–5.00, Ps<0.05). Poorer self-reported health status (ORs 0.90–0.94, all Ps<0.05), favourable attitude towards drug advertising (ORs 1.34–1.61, all Ps<0.001) and searching for medical information online (ORs 1.32–2.35, all Ps<0.01) predicted all self-reported behavioural outcomes. Older age (ORs 1.01–1.02, Ps<0.01), less education (OR 0.89, P<0.01), lower income (ORs 0.89–0.91, Ps<0.05) and higher materialism (ORs 1.02–1.03, Ps<0.01) also predicted one or more self-reported responses.ConclusionsTaken together, the findings suggest individuals, especially those who are ‘at-risk’ (ie, with poorer self-reported health status, older, less educated, lower income and ethnic minorities), may be more vulnerable to drug advertising and may make uninformed decisions accordingly. The outcomes raise significant concerns relating to the ethicality of drug advertising and suggest a need for stricter guidelines to ensure that drug advertisements provided by pharmaceutical companies are ethical.