Background: The process of demographic and epidemiological transition that occurred in Chile during the second half of the 20th century has been broadly described, with special emphasis in adults diseases. Objective: Characterize the process of epidemiological transition in infancy, using as model a disease that affects exclusively this age group (i.e. childhood cáncer). Method: The trend of childhood cáncer mortality rate and its proportion of deaths in relation to other diseases was analyzed for the period 1960-2000. Results: Childhood cancer mortality rate reduced 41.4% between 1960 and 2000 (5.8 to 3.4/100 000 children younger than 15-years old), mainly as a consequence of important advances in technology and public health organization. On the contrary, childhood cáncer proportion of deaths increased 11-fold during the same period of time (4 to 43/1 000 children younger than 15 years-old), mainly as a consequence of reduction in transmittable diseases and malnutrition mortality rates. Conclusión: Knowing the characteristics of the epidemiological transition in infancy implies important changes and challenges for the Chilean pediatrician of the 21st century, whose professional practice will be performed in a different scenario compared to the mid-20th century.