This paper briefly describes Cuban immigration to the United States since the late 1800s, and examines the available demographic and social adjustment data for the latest group of immigrants--the approximately 125,000 persons who came by sea from Mariel Harbor in 1980. The latest wave of Cubans is characterized as poorer, less educated, and less job ready than previous immigrants. In addition, when compared with Cubans already living in the United States, recent arrivals are said to (1) comprise more single individuals, (2) be predominantly male, (3) be younger, and (4) be disproportionately Black or Mulatto. However, the widely believed assertion that the group is largely made up of homosexuals, criminals, and deviants is disputed. Finally, adaptation problems of the Mariel Cubans are discussed in the areas of mental health, housing, and employment. The author concludes with speculation as to the effects on Miami's Cuban American community of the new immigrants, especially given the number of Blacks among the Mariel group and the widespread racial prejudice among earlier immigrants. (GC)