Detailed qualitative case studies of four early childhood special education programs, representing a variety of approaches to decision making as well as different community settings (urban, suburban, and rural), present information regarding their diagnostic assessment procedures. In general, programs reported that the main objective of diagnostic assessment is to ascertain the child's eligibility for special education services. Programs tended to focus on identifying children who were mildly handicapped, as more severely handicapped children had already been identified and were being served by other programs. Referrals for diagnostic assessment came from a variety of sources, including the Preschool Screening program, physicians, parents, and community agencies. All programs had structured screening programs that refer children to the diagnostic assessment process. A state-mandated formation of interagency collaboration committees was being implemented in all programs to promote interagency collaboration, exchange of information and service delivery, and to reduce duplication of services. All programs also included some sort of parent involvement. Assessments varied among the programs, ranging from a minimum of one hour to a more extensive 6-week diagnostic placement. The number of personnel involved in the diagnostic assessment process ranged from 3 to 8 among programs. Variation in the use of diagnostic assessment techniques was evident. (CB)