Objectives The purpose of this study was to assess reproductive outcomes, especially birthweight, and the consumption of fatty fish from the Baltic Sea, contaminated with persistent organochlorine compounds, among women from the Swedish east coast.Material and methods Cohorts of fishermen's wives from the Swedish east and west coasts were established, and linked to the Swedish Medical Birth Register for 1973--91; 1501 children were born in the eastcoast cohort and 3553 in the westcoast cohort. Comparisons were made with regional populations, and between the cohorts. Dietary interviews were made with 69 randomly selected women from the cohorts and 69 referents.Results The women interviewed from the east- and westcoast cohort women ate locally caught fish more than twice as often as their referents. Compared with the regional population the eastcoast cohort women gave birth to an increased number of infants with low birthweights (< 3000 g), whereas the opposite was seen in the westcoast cohort. Infants in the eastcoast cohort had significantly lower birthweights than infants from the westcoast cohort (medians 3530 g versus 3610 g, P