In Alabama between 1985 and 1989, a total of 94 physicians outside of the four largest cities in the state dropped the obstetrics portion of their practices or left practice in their communities altogether. During the same period 82 physicians entered obstetrics practice in this area. The study presented here used survey and archival data to compare practice characteristics of generalists and specialists in rural and town counties who made different decisions about providing obstetrics care. More generalists left and more specialists entered practice both in town and in rural counties. Rural counties lost more obstetrics providers because more generalists provided the obstetrics care in these areas. Across both specialty and county categories, physicians in group practice who accepted Medicaid and had local access to larger numbers of patients were more likely to remain or begin new obstetric practices. During this period, some obstetrics specialists moved into rural communities that had previously supported only generalist physicians. These findings suggest that the options for organizing successful obstetrics practices have narrowed, putting solo and generalist physicians who operate small-scale obstetrics practices at a disadvantage. These physicians also face competition from obstetrics specialists who are beginning to enter practice in the rural areas of the state. Designing policies that effectively improve geographic access to care requires a realistic understanding of the practice constraints faced by obstetrics providers. For example, as centralized specialist group practices serve residents from surrounding rural areas, programs that facilitate linkages, such as satellite clinics and use of mid-level practitioners, can be promoted.(ABSTRACT TRUNCATED AT 250 WORDS)