If surveys are the most multi-purpose of all research designs, case studies are probably the most flexible. At the simplest level, they provide descriptive accounts of one or more cases. When used in an intellectually rigorous manner to achieve experimental isolation of selected social factors, they offer the strengths of experimental research within natural settings. In between these two extremes there is an extended range of case studies combining exploratory work, description and the testing out of hunches, hypotheses and ideas in varying combinations. The case study is the social research equivalent of the spotlight or the microscope: its value depends crucially on how well the study is focused.