The IWCT2015 is to be held in conjunction with ICST2015 focusing on combinatorial testing. The workshop welcomes academic research submissions, as well as industrial experience reports. Combinatorial testing (CT) is a widely applicable generic methodology and technology for software verification and validation. In a combinatorial test plan, all interactions between parameters up to a certain level are covered. For example, in the special case of pairwise testing, for every pair of parameters, every pair of values will appear at least once. Studies show that CT is more efficient and effective than random testing and expert test selection methods. CT has gained significant interest in recent years, both in research and in practice. However, many issues still remain unresolved, and much research is still needed in the field. For example, while pairwise testing is a well recognized and popular test planning method, investigations of actual failures in a number of software and systems convincingly show that pairwise testing may not be sufficient so the less-studied high strength CT (i.e., t-way for t>2) may be needed. In addition, combinatorial test suites must exclude invalid combinations of test values, limiting the degree of freedom the algorithms have, thus complicating the problem. Moreover, modeling languages and tools for easily capturing the input test space are also required for real-life applicability of CT. Other obstacles for wide acceptance of CT in industry are the gap between the generated test plans and executable tests, and the difficulty in determining expected results for the generated tests. Finally, empirical studies on CT, as well as thorough comparison with other methods are also required. In this workshop, we plan to bring together researchers actively working on combinatorial testing and create a productive and creative environment for sharing and collaboration. Researchers attending the workshop will have an opportunity to publish their work in a dedicated venue, forge collaborations and take active parts in the growing community of researchers working in the field. The workshop will also serve as a meeting place between academia and industry, uniting academic excellence with industrial experience and needs. This will allow participants from academia to learn about the industrial experience in practical applications of CT to real-life testing problems, and together with the colleagues from industry identify the pain points that are obstacles to wider applications of CT that should be addressed in future research. Industrial participants will have opportunities to meet the leading scientists in the field and learn of the latest advances and innovations.