A series of studies were conducted to modify the General Aptitude Test Battery (GATB) and the Minnesota Importance Questionnaire (MIQ) for use with mentally retarded individuals. Modification of the GATB consisted of eliminating answer sheets, increasing practice, individual administration, untimed administration, removal of verbally loaded items, and simplifying test instructions and practice problems. None of these modifications significantly changed the test performance of the mentally retarded subjects. Modification of the MIQ involved rewriting the item stems at a readability level which was understandable to mentally retarded individuals. Form S, the revised 17-scale MIQ, was found equivalent to the standard MIQ in terms of profile similarity and, for 11 of 17 scales, equivalent means and standard deviations. Individual differences in measured abilities and needs among the mentally retarded were found to approximate those of the non-mentally retarded. Applicability of the Theory of Work Adjustment, utilizing the GATB and Form S MIQ in assessing work personalities, is indicated for mentally retarded individuals in the borderline and, to a lesser extent, the mild categories. (Author)