Interpersonal conflict between software developers and testers is inevitable and pervasive. This conflict is likely to be negatively associated with software quality and job satisfaction. This study addresses one major research question: What are the sources of interpersonal conflict between developers and testers in software development? Using a qualitative approach, we collect and analyze fifty developer-tester conflict scenarios from professional developers and testers. Preliminary results indicate that conflict sources between software developers and testers fall into three major categories: Process, people, and communication. Conflict sources are presented in a category-subcategory-example format. Implications for research and practice are discussed.