A cross-sectional survey was carried-out in 1978 in Rio Grande do Sul, the southernmost state of Brazil (population: about 8,000,000 inhabitants in 1978). The state was divided into four strata, each one being a district geo-economic area: Porto Alegre, the state capital-Metropolitan Belt, including 13 counties around Porto Alegre; Urban Interior, the non-metropolitan urban areas of the state; Rural Interior, composed of all non-urban areas outside the Metropolitan Belt. In each stratum a probability sample was selected in multiple stages. A total of 2.056 households were successfully contacted (94.7% of the 2.172 households selected). This article presents an analysis of migration between the four strata and its relation with blood pressure. The lowest blood pressure level was found in the Rural Interior, and the highest in the Metropolitan Belt. The mean diastolic blood pressure was about the same in each stratum for migrants and non-migrants. Both residents in Porto Alegre and Metropolitan Belt born in the Rural Interior were found to have higher mean blood pressure than non-migrants of the Rural Interior. On the other hand, persons who migrated within the rural stratum (from one rural area to another) were found to have a low blood pressure level, not differing from the non-migrants. Migrants from the Rural Interior, residing in urban areas were found to have blood pressure levels that increased with the period of time since migration.
