As with any new theory, it is necessary to validate the basic construct of vocational maturity. Once this is done, instruments to measure vocational maturity, or decision making, can be evaluated. With this as an objective, this paper discusses some of the problems associated with measuring vocational maturity, such as identifying variables, methods of data collection, and item selection procedures. The selection and definition of related vocational maturity variables is complicated by the lack of a well-defined taxonomy. Choice of methodology is difficulty, since three approaches have been used in previous data gathering--the partially structured interview, the structured interview, and fixed alternative questions. The paper also examines the basic assumptions regarding vocational maturity as well as validation by internal and external evidence. Validation by internal evidence is discussed in terms of the four dimensions of Crites' model: (1)Consistency of Vocational Choice, (2) Wisdom of Vocational Choice, (3) Vocational Choice Competencies, and (4) Vocational Choice Attitudes. Validation by external evidence presents problems in that the existing data regarding external evidence is somewhat limited at the present time. (JS)