The paper examines issues, philosophy and guidelines for psychological assessment of the disabled. Focused on are: (1) adjustments in testing procedures and (2) applicability of standard norms with commonly used psychological test instruments for the assessment of ability, interest, and personality. The importance of accurate assessment for appropriate rehabilitation program development is stressed. Considered as inappropriate are the approach which rejects all standardized testing procedures and norms as unfair as well as the approach which applies standard instruments with no modifications. A functional approach is recommended which emphasizes standardization, normative validity and reliability considerations placed in the context of the whole person including a careful interview covering personal, social, and vocational history. Problems with using the General Aptitude Test Battery are specifically identified and the lack of standardization data for the disabled on many other tests is noted. (DB)