Substantial evidence now supports the use of virtual worlds for teaching, learning, and more recently, assessment. Developing assessment activities for virtual worlds is inherently complex due to the open-ended, exploratory nature of a 3-D immersive environment. This study developed a framework for designing activities that produce evidence of students’ levels of proficiency for a defined set of knowledge, skills, and abilities (KSAs). The framework is based on Evidence-Centered Design and enables the designer to articulate and define the linkages between student tasks, observable variables, evidence, scoring, inter-relationships, and KSAs. Two methods were used to test the efficacy of the framework: observation and logdata. Initial results support the use of the framework to systematically design virtual world assessment activities.