Although Hispanics' use of breast cancer screening services has been investigated, to date there have been no published studies of distinct Hispanic populations in different areas of the country. Using the diverse populations and sites involved in the National Hispanic Leadership Initiative on Cancer 'En Acción', this study examines ethno-regional differences in breast cancer screening rates among these groups and explores the correlates of screening participation. Data collected through telephone surveys were analyzed for women 40 years of age and older (n = 2082). After controlling for demographic variables traditionally related to breast cancer screening rates, it was found that ethno-regional differences in breast cancer screening practices clearly persisted. In addition to traditional demographic factors, other variables evidently underlie differences in Hispanics' utilization of breast cancer screening services. These variables may be cultural and should be investigated in future research. Meanwhile, researchers should not refer to the 'Hispanic' population at large without identifying, addressing and clarifying the ethno-regional characteristics of their samples.