Background Adherence to prescribing guidelines varies between primary health care units. The aim of the present study was to investigate correlations between characteristics of primary health care units and adherence to prescribing objectives for rational drug use with focus on drug information from the pharmaceutical industry. Methods A cross-sectional study was performed in all 25 primary health care units in Göteborg, Sweden. A questionnaire on characteristics of practice settings [(i) size of unit, (ii) profession of head, (iii) use of temporary physicians, (iv) drug information from the pharmaceutical industry, (v) producer-independent drug information, and (vi) education on prescribing for newly employed physicians] was sent to the heads of the units. A national sales register for prescribed drugs (Xplain) was used for evaluation of adherence to the six regional prescribing objectives concerning proton pump inhibitors (PPIs), angiotensin converting enzyme inhibitors (ACEIs), statins and antidepressants. Results Twenty-two out of 25 primary health care units responded to the questionnaire (response rate 88%). A physician as head and presence of producer-independent drug information was positively correlated with adherence to the prescribing objectives (median number of prescribing objectives adhered to (25th - 75th percentile): 2.5 (1-3.25) vs 1 (0-2), P = 0.013; 2 (1-3) vs 0, P = 0.043, respectively. Presence of drug information from the pharmaceutical industry and education on prescribing for newly employed physicians was negatively associated with adherence to the prescribing objectives: 1 (0-2) vs 3.5 (2.25-4.75), P = 0.005; 1 (0-2) vs 3 (1.5-4), P = 0.034, respectively. Conclusion Several characteristics of the primary health care units correlated with adherence to prescribing objectives for rational drug use. Further research on this topic is needed and would constitute valuable information for health care decision makers.