The purpose of this document is to suggest guidelines for the identification and assessment of children who should participate in programs related to the infant-toddler (Part H) and the preschool (Part B, Section 619) components of Public Law 99-457, the Education of the Handicapped Amendments of 1986. The guidelines integrate information from the fields of medicine, health care, social services, psychology, and education and describe practices to advance the field of early intervention and improve services to children and families. The document first describes the requirements of Public Law 99-457 regarding screening and assessment. A theoretical viewpoint about childhood development is presented, and the differences between screening and assessment are outlined. The complex factors involved in defining the population to be served by Public Law 99-457 are noted, and guidelines for screening and assessing young disabled and developmentally vulnerable children are then proposed. A sequenced planning process is outlined and future tasks are listed. Appendices are attached that contain illustrations of several different models, representative lists of screening and assessment instruments and procedures, a glossary, and regulations from Public Law 94-142 and Public Law 99-457 that pertain to screening and assessment. Includes 79 references. (JDD)