Despite agreement that children's social functioning may be the best indicator of current and future behavioural and emotional problems, its measurement is under-developed. Measures of social functioning and psychopathology remain entangled, although this may be less critical clinically than in research. Confusion in terminology and definition is highlighted and clarified by tracing diverse but converging areas of research. Current measurement needs and approaches are presented along with six measures—each suited to different assessment needs. It is suggested that the next generation of instrument developers make use of findings from studies of social competence and motivation, focusing not only on social skills and deficits but also on beliefs and goals that lead to adaptive and maladaptive functioning.