Background: Coordinated health service utilisation in the ambulatory care sector is of major interest from a health policy perspective. This ecological study investigates the interplay between medical care utilisation in hospital outpatient departments and in freestanding physician practices by drawing on the example of the Austrian healthcare system, which is standing out due to three features: ambulatory care is provided by both free-standing public (contract) and private (non-contract) practitioners; medical specialists operate in free-standing physician practices and in hospital outpatient departments; essentially, no gatekeeping is in place. As the ongoing health care reform aims to strengthen the primary care sector, we investigate whether in the current system care in general practitioner and specialist physician practices is in a substitutive, complementary or independent relation with medical care in outpatient departments. Methods: Hypotheses were tested using ordinary least square regression analysis based on administrative data of all Austrian districts with a hospital department in 2010, including a proxy for actual utilisation rather than physician headcount. Results: Controlling for socio-demographic and geographic characteristics and inpatient activity, we find that a higher level of care provision by contract GPs is associated with lower use of hospital outpatient departments on the district level. In contrast, a higher level of care by non-contract specialists is related to a higher utilization in outpatient departments. Conclusion: While care by non-contract specialists seems to be in a complementary and potentially demand-inducing relation with outpatient departments, primary care by contract GPs appears to be capable of replacing care in outpatient departments.