Objective: Out-of-pocket costs strongly affect patient adherence with medicines. For asthma, guidelines recommend that most patients should be prescribed regular low-dose inhaled corticosteroids (ICS) alone, but in Australia most are prescribed combination ICS-long-acting β2-agonists (LABA), which cost more to patients and government. The present qualitative study among general practitioners (GPs) explored the acceptability, and likely effect on prescribing, of lower patient copayments for ICS alone. Methods: Semistructured telephone interviews were conducted with 15 GPs from the greater Sydney area; the interviews were transcribed and thematically analysed. Results: GPs reported that their main criteria for selecting medicines were appropriateness and effectiveness. They did not usually discuss costs with patients, had low awareness of out-of-pocket costs and considered that these were seldom prohibitive for asthma patients. GPs strongly believed that patient care should not be compromised to reduce cost to government. They favoured ICS-LABA combinations over ICS alone because they perceived that ICS-LABA combinations enhanced adherence and reduced costs for patients. GPs did not consider that lower patient copayments for ICS alone would affect their prescribing. Conclusion: The results suggest that financial incentives, such as lower patient copayments, would be unlikely to encourage GPs to preferentially prescribe ICS alone, unless accompanied by other strategies, including evidence for clinical effectiveness. GPs should be encouraged to discuss cost barriers to treatment with patients when considering treatment choices. What is known about the topic?: Australian guidelines recommend that most patients with asthma should be treated with low-dose ICS alone to minimise symptom burden and risk of flare ups. However, most patients in Australian general practice are instead prescribed combination ICS-LABA preventers, which are indicated if asthma remains uncontrolled despite treatment with ICS alone. It is not known whether GPs are aware that the combination preventers have a higher patient copayment and a higher cost to government. What does this paper add?: This qualitative study found that GPs favoured combination ICS-LABA inhalers over ICS alone because they perceived ICS-LABA combinations to have greater effectiveness and promote patient adherence. This aligned with GPs' views that their primary responsibility was patient care rather than generating cost savings for government. However, it emerged that GPs rarely discussed medicine costs with patients, had low knowledge of medicine costs to patients and the health system and reported that patients rarely volunteered cost concerns. GPs believed that lower patient copayments for asthma preventer medicines would have little effect on their prescribing practices. What are the implications for practitioners?: This study suggests that, when considering asthma treatment choices, GPs should empathically explore with the patient whether cost-related medication underuse is an issue, and should be aware of the option of lower out-of-pocket costs with guideline-recommended ICS alone treatment. Policy makers must be aware that differential patient copayments for ICS preventer medicines are unlikely to act as an incentive for GPs to preferentially prescribe ICS alone preventers, unless the position of these preventers in guidelines and evidence for their clinical effectiveness are also reiterated.