Scenario based approaches are becoming ubiquitous in systems analysis and design but remain vague in definition and scope. A survey of current practices indicates we must offer better means for structuring, managing, and developing their use in diverse contexts. The European Esprit project Crews (Cooperative Requirements Engineering with Scenarios) are seeking a deeper understanding of scenario diversity, necessary to improve methodological and tool support for scenario based requirements engineering. They follow a two pronged strategy to gain this understanding. First, following the "3 dimensions" requirements engineering framework developed in the precursor Nature project (K. Pohl, 1994), they developed a scenario classification framework based on a comprehensive survey of scenario literature in requirements engineering, human computer interaction, and other fields. They used the framework to classify 11 prominent scenario based approaches. Secondly, to complement this research framework, they investigated scenario applications in industrial projects through site visits with scenario user projects. The article focuses on these site visits. It was found that while many companies express interest in Jacobson's use case approach, actual scenario usage often falls outside what is described in textbooks and standard methodologies. Users therefore face significant scenario management problems not yet addressed adequately in theory or practice, and are demanding solutions to these problems.