An attempt is made to develop models that can explain the age patterns of infant and child mortality. The authors first review factors affecting infant and child mortality, identifying both the factors involving exposure to risk and those governing the individual's resistance to disease. Consideration is also given to the effect of therapeutic care. An indicator of the structure of child mortality is then developed to be "used as a dependent variable in a model of linear regression which includes mortality level, sex, climate, time and income as explanatory variables." The results indicate that the mortality level is the key factor affecting the age pattern of mortality during childhood and that the mortality of both sexes is very similar between one and five years of age. Of the other factors considered, only climate has a significant impact on mortality. (summary in ENG, SPA)