This is a retrospective study of mothers charged with killing their children within 24 h of birth in the city of Rio de Janeiro, Brazil. Characteristics of the mothers and the victims, the circumstances surrounding the offense, the mothers' motivation and state of mind at the time of the offense, the legal process, and follow-up data were investigated. We analyzed our cohort as two sub-groups: 26 offenses that occurred between 1900 and 1939 and were dealt with under the Brazilian Penal Code of 1890, and 27 offenses that were committed between 1940 and 1995 and were dealt with under the Penal Code of 1940. The mothers were young (mean 22.5 +/- 5.3 years), unmarried (88.2%), non-Caucasian (73.8%), and had limited formal education. They usually kept the pregnancy a secret (94.1%) and gave birth in a classified way (100%). Most victims were killed through wounding violence (77.4%). Offenders identified between the years of 1940-1995 had increased rates of literacy (chi 2 = 6.80, d.f. = 1, p = .009), a higher incidence of reported psychiatric symptoms (chi 2 = 11.82, d.f. = 1, p < .001), increased referral for psychiatric assessment (chi 2 = 3.85, d.f. = 1, p = .05), and greater frequency of cases where statute of limitations was expired (chi 2 = 3.88, d.f. = 1, p = .049).