This paper attempts a critical review not so much of the concept of locus of control as the plethora of unidimensional or sphere-specific measures that have been developed in the past 25 years. After a brief history of the development of the concept of locus of control, various oft-repeated and some new criticisms are considered. One frequent response to problems associated with the original concept and scale has been to develop new psychometrically validated, sphere- or topic-specific measures. These are tabulated and reviewed under five headings: measures (either multidimensional or sphere-specific) of the general concept of locus of control; measures devised specifically for children and adolescents; measures that have concentrated on aspects of mental and physical health; work, career and economic locus of control measures; and finally, measures which have extended the locus of control concept into other areas. The advantages and disadvantages of this proliferation of measures is considered in some detail, especially the issue of incremental validity, and recommendations are made for future work in this area.