BACKGROUND: A majority of doctor-patient meetings result in the patient getting a prescription. This underlines the need for a high-quality prescription process. While studies have been made on single therapeutic drug groups, a complete study of the physicians' general thought process that comprises the prescription of all drugs still remains to be made. OBJECTIVE: To identify variations in ways of understanding drug prescribing among GPs. METHODS: A descriptive qualitative study was conducted with 20 Swedish physicians. Informants were recruited purposively and their understandings about prescribing were studied in semi-structured interviews. Data were analysed using a phenomenographic approach. RESULTS: Five categories were identified as follows: (A) GP prescribed safe, reliable and well-documented drugs for obvious complaints; (B) GP sought to convince the patient of the most effective drug treatment; (C) GP chose the best drug treatment taking into consideration the patient's entire life situation; (D) GP used clinical judgement and close follow-up to minimize unnecessary drug prescribing and (E) GP prescribed drugs which are cheap for society and environmentally friendly. The categories are interrelated, but have different foci: the biomedical, the patient and the society. Each GP had more than one view but none included all five. The findings also indicate that complexity increases when a drug is prescribed for primary or secondary prevention. CONCLUSIONS: GPs understand prescribing differently despite similar external circumstances. The most significant factor to influence prescribing behaviour was the physician's patient relation approach. GPs may need to reflect on difficulties they face while prescribing to enhance their understandings.