Mainstreaming decisions, including identification of handicapped students for regular class placement and support service recommendations (e.g., reduced class size, inservice training, consultation services), are frequently made by nonclassroom personnel such as school psychologists, occupational/physical therapists, and speech/language pathologists. Factors considered by these professionals in making mainstreaming decisions are poorly understood, however. This study sought to identify mainstreaming modifications judged to be important by ancillary professionals in recommending mainstreaming of students with mild exceptionalities. Data revealed that no significant differences were noted in number of selected modifications as a function of diagnostic category. Ancillary staff members indicated, however, that substantial modifications were needed to facilitate successful mainstreaming. Results are discussed relative to current educational trends.