Narrative text, tables, and maps summarize information derived from a random sample of 20% of the Migrant Student Record Transfer System (MSRTS) data base as it existed in June 1976 related to the mobility patterns of migrant children in the contiguous United States and Puerto Rico from January 1975 to April 1976. The data base is a tabulation of to/from information for migrant children enrolled in different states on each of the two dates of any one of various pairs of selected dates. Some limitations are deemed inherent, for instance: (1) data may be distorted by generalizing findings where the number of moves was small, (2) the MSRTS data base shows 117,000 "transactions" for the 20% sample, (3) there is no way to distinguish a school withdrawal caused by an interstate move from a withdrawal caused by some other factor, (4) enrollment of migrant children in nonproject schools during parts of the year are not usually recorded on the MSRTS, (5) most interstate moves by migrant children take place during the summer; (6) children may have been in different statuses at various times in the 15 months covered. Included is a grouping of states into regions on the basis of common patterns of interchange of migrant children, summary of moves to/from each state, brief analysis of 300 individual migrant student records systematically selected from the 20% sample and an analysis of school enrollment data on 7-, 8-, and 9-year-old migrant children. (AN)