A study investigated the functional relationship that exists when mental ability and language competence are separately and simultaneously measured with regard to their influence on the effective treatment of verbal information. Data were gathered from 100 men and women, aged 20-60, who were tested for language competence, reading comprehension, intelligence, and writing ability. Results revealed that syntactical skills were the major component for assessing English composition; and that skill in the use of language was of greater significance than was mental ability in the treatment of verbal information, particularly in exercises which call for critical analysis and the making of sound judgments. The findings suggest that the assessment procedures used in this research may be a feasible means of judging the quality of adults' written language. (Twenty tables of data are included; 166 references and eight appendixes containing testing materials are attached.) (Author/KEH)