We investigated the association between breast feeding, economic factors and conviction for violent delinquency by age 25 years among subjects of the 1982 Birth Cohort from Pelotas, Southern Brazil. Information on breast-feeding pattern and duration was collected in childhood, during the 1983, 1984 and 1986 follow-ups. Information on socio-economic and family characteristics was also obtained between 1982 and 1996. Of the 5914 livebirths enrolled in the cohort, 5228 had obtained an identification document within the state of Rio Grande do Sul, and could thus be identified in judiciary databases. The outcome studied was conviction due to a violent act between ages 12 and 25 years. A total of 106 young people had been convicted at least once (3.0% of men and 1.0% of women). Subjects born to black or mixed mothers and coming from low-income families were at higher risk of having been convicted. Neither crude nor adjusted analyses showed any association between breast feeding and conviction for violent delinquency. Violent delinquency apparently depends more on social factors than on individual factors such as breast feeding.