The complex relationship between sociocultural variables, such as ethnicity, language, and working status, and the utilization of facilities for perinatal health care were explored in a predominantly Mexican American community in Chicago. The project, which was initiated in 1977, was designed to provide objective data on utilization patterns of perinatal health facilities and to assess the importance of the migratory experience on the utilization of perinatal services among Mexican immigrants and Mexican Americans living in the community. Patterns of utilization of perinatal health facilities by pregnant women, preference for the ethnicity, language, and sex of the health care provider, and different patterns that influence the months of prenatal care were examined in the context of the migration factor. An interview instrument was developed to include both quantitative and qualitative data. Ages among the sample of women ranged from 16-41. 60 women were immigrants born in Mexico and 29 women were Mexican Americans born in the US. Women in the sample were using 2 major health care "tracks" for their perinatal care: public facilities for prenatal care, delivery, and pediatric care for the infant; and private physicians for prenatal care, pediatric care, and delivery in the small, Catholic hospitals where the physicians tended to have admitting privileges. 34 women were attending private facilities, and 55 women were using public facilties. 27 women (30.3%) cited economic considerations as the reason for choosing a physician or facility. Other reasons included personal referral or recommendation (27%), previously used (16.9%), and geographic proximity (6.7%). The use of public prenatal clinics correlated significantly with the citing of economic considerations as the basis for choosing this type of care. 32 women (36%) were working during their pregnancy. There was a significant relationship between choosing a private physician for prenatal care and being employed. Women who were recent immigrants, as well as Mexican Americans, tended to use public facilities. Mexicans who had been in Chicago for more than 2 years tended to use private facilities. The length of time since a woman left Mexico correlated negatively with the month of prenatal care. Traditional patterns of postpartum behavior were found to be persistent among the migrant women regardless of the time of migration and were found to be present among Mexican Americans.