This empirical study investigates factors that influence the implementation of science inquiry in the education systems of Turkey, Israel, Sweden and the Czech Republic. Data was collected by means of recordings of science experts' discussions as part of an EU-funded project called Science-Teacher Education Advanced Methods (2009-2012). Results of the qualitative analysis reveal that the following general indicators provide insight into the extent of implementation of inquiry-based science education (IBSE): (1) curriculum (2) assessment (3) policy and (4) teacher professionalization systems. In a second step comparative analyses of the four countries' education systems were conducted with regard to these indicators. To compare these factors we refer to both the framework of neo-institutional theories that explore the emergence of isomorphic educational models and to results from comparative studies emphasizing the influence of the countries' individual structure and cultural practices on modifying global pressure to convergence. Results show that in each of the countries these indicators influence the implementation of science inquiry to varying degrees. Moreover, as a result of the comparative analyses further country specific factors important for implementing science inquiry were found: (5) the need to improve existing teaching methods, (6) predominant teaching patterns, (7) infrastructure that enables changes in education and (8) education system's general goals that correlate with reforms.