Described are the diagnostic procedures employed for multiply and visually handicapped children 3-12 years of age functioning at the preschool level at the Boston Center for Blind Children. Diagnosis is seen to serve as a key to understanding the child and as a basis for planning services. Described is the center setting which serves six multiply handicapped children 4 days a week with a staff of one teacher and two teacher aides. Explained are prestudy procedures including referral, application for admission, arrival, and presence of one parent (usually the mother) throughout the diagnostic study. Noted are the roles of each of the following staff members in the diagnosis: the social worker (who interprets the family situation and serves as a parent advocate), the pediatrician (who interprets medical findings in nontechnical terms to team members), the psychiatrist (who focuses on the whole child from a psychiatric viewpoint), the educator (who observes the child and orders the child's needs as priority items), the psychologist (who focuses on the child's level and mode of functioning through psychological evaluations). The 6- to 7-day diagnostic study is said to culminate in the diagnostic case conference at which staff members present their findings and plan treatment procedures. (DB)