The study investigated the reliability and validity of professional groups using the Modified Component Disability Instrument to identify/evaluate learning disabled (LD) adolescents. Ss included 166 LD teachers, speech clinicians, remedial reading teachers, school psychologists, school principals, and school counselors. Calculations were made for temporal reliability, cross validation, and construct validity. Temporal reliability data suggested that the instrument is a reliable measure as it assesses components related to LD students. It was concluded from cross validation results that the probabilities provided by the LD teacher and speech clinician groups are not significantly different. The validity phase of the study showed that, with limited exceptions, the instrument is valid for its logical constructs both between and within LD and nonLD groups. Tables with statistical data and a copy of the Modified Component Disability Measure are included. (SB)