The 1954 "Brown v. Board of Education" decision laid the basis for dismantling de jure racial segregation of schools and resulted in a 50 percent reduction in the number of schools in which black students composed 90 to 100 percent of the enrollment between 1968 and 1980. "Brown" represented a significant shift in the national attitude toward blacks and was an important advance in intergroup relations. However, in the last decade the proportion of black students enrolled in many large educationally deficient urban schools has been rising, resulting in racial isolation and de facto segregation. Desegregation appears to have resulted in a small improvement in black students' reading skills but no significant change in their mathematics skills. Some evidence has begun to accumulate indicating that desegregation may break a generational cycle of segregation and racial isolation by influencing such important adult outcomes as college graduation, income, and employment patterns, but the measured effects are weak and appear to be dependent upon sex and geographic region. Studies of the effect of desegregation on intergroup attitudes are generally inconclusive and inconsistent; and no studies have focused on changes in intergroup behavior, despite indications that desegregated schooling can provide students with valuable behavioral experience that prepares them to function in a pluralistic society. School desegregation policies and practices can also have marked and predictable effects on intergroup relations. A list of 186 references is appended. (FMW)