A sample of deaths among children under one year of age in the Metropolitan Region of Rio de Janeiro was studied for a twelve-month period and the information provided by the death certificates was complemented with data obtained from hospital handbooks and interviews with the children's mothers. It was observed that the percentage of infant deaths occuring outside the hospital environment is 13% (4% for the neonatal period and 23% for the post-neonatal one), and hence underestimated by the official statistics. This particular group of deaths was analysed in relation to the main groups of causes, areas of residence, necropsy and search for health services. Pneumonia was the major death cause in the post-neonatal group, with 40% of the deaths occuring outside the hospital. The areas of residence which preserved a high proportion of such deaths are area 1 (Southern Zone) for the neonatal group and area 7 (Niterói and São Gonçalo) for the post-neonatal one. Necropsy in these deaths presented a low percentage (43% for neonatal deaths and 65% for post-neonatal). In 38% of the neonatal deaths and in 63% of the post-neonatal ones the mothers looked for health services in the week preceding the death, but even so these children failed to have their deaths assisted or even prevented.