This document discusses the development of a measure called the KEY-measure to evaluate the effectiveness of adult social work in Finland. It describes a project that tested the use of single-case evaluation designs to measure goal attainment and the impact of social work methods and contextual factors. The project found that single-case evaluation fits well for adult social work but that social workers found it difficult to incorporate systematically. The document presents results of testing the KEY-measure which showed what types of goals were commonly set, levels of goal achievement, and influential contextual factors. It concludes that more work is still needed to develop an effective program theory for evaluating adult social work.