CASCAID was conceived as a support tool for the use of LEA Careers Officers carrying out their appointed task of giving vocational guidance to students in secondary schools. The system arose out of the situation in which the practising Careers Officer finds himself; that of attempting to assimilate the plethora of information of which he should be aware, mentally processing this information in the interview situation, and producing realistic advice to his client. It is a very practical system, based on real needs and circumstances. It is not a guidance technique in itself nor does it predicate a particular guidance theory. Nationally, at the present time, there are often neither the resources within the Careers Service nor the vital preliminary careers education programme within the schools to provide the level of careers preparation which we would all wish. It is in this context that the usefulness and effectiveness of CASCAID has to be assessed. The present paper describes the development of the system up to and including its transition to CASCAID II, and describes its principal features.