The death causes of children under one year of age in the city of Salvador, Brazil, between 1962 and 1971, including a statistical investigation of the secular tendency of the infant mortality rate, were reviewed. For some data a straight line was adjusted with a mathematical equation of the type Y = a + bx (method of the least squares). For other a modified exponential curve of the type Y = k + ab x was used. The general tendency of the infant mortality rate was descendent throughout the period 1962 to 1970, arising in 1971 to levels observed in 1964. A similar fact was encountered when neonatal mortality and mortality rates by gastroenteritis and other diarrheal diseases were studied.
Mortality; Infant Mortality; Secular tendency