This paper reports the results of a study on neonatal mortality in the State of Rio de Janeiro (1979-1993), according to major causes of death, by age and region of residence. The authors suggest criteria for grouping neonatal deaths according to causes, taking into consideration frequency and preventability. For deaths which occurred in the first day of life, immaturity and fetal growth retardation were the only causes of death that showed significant decline. An increase in deaths due to respiratory affections of the fetus and newborns was observed. Causes of death said to be reducible by "adequate control of pregnancy and attention at delivery" and "early diagnosis and treatment" remained unaltered. The authors noted that a decrease in death rates took place starting with the 1-6 day age group. The comparison with other countries called attention to the high rates of neonatal death in Rio de Janeiro. It also pointed out an increase in the proportion of deaths classified as "respiratory problems of the newborn", demonstrating lack of specificity in defining the basic cause of death.