This study relates the residential segregation or ghettoization of the Puerto Rican population in New York City to the employment opportunities, mobility and assimilation of the minority. Both ecological and individual level approaches are utilized to investigate three basic questions: (1) What are the mechanisms of the influence of ghetto residence on the employment, mobility and assimilation of Puerto Ricans in New York City? (2) Are there age, sex, educational, etc. differences in the effects of ghetto residence on the employment, mobility and assimilation of New York's Puerto Ricans? (3) Do the journey-to-work and residential migration experiences of upwardly-mobile Puerto Ricans demonstrate means of overcoming the negative influences of residential segregation? Three basic data sets are used in the study, each with particular strengths and weaknesses. First of all we consider a selected group of tracts from the 1960 Census of the New York SMSA. A second data set, taken from the 1968-69 New York Urban Employment Survey, allows the examination of the negative influences of residential segregation on an individual level. Finally, the journey-to-work patterns and the recent residential mobility experiences of a group of families from a Catholic parish in the Bronx are examined in a third part of the study. (Author/JM)