RESUMEN
In an attempt to elucidate the causes which led to the high percentage of HIV infection in the infantile population in Romania, the paper deals with the study of the evolution of the infection process, in the 0-6 years age group; the process was separately studied in children from closed collectivities (5,318 sera) and children living with their families (2,462). The study of the various patterns obtained with sera analysed by western-blot allowed of concluding that the massive spreading of the infection in both types of infantile population occurred in 1991-1992, the most intense process being reported in the 0-2 years age group (children from closed collectivities). The differences between the evolution of HIV infection epidemic in the above mentioned infantile populations and that noticed in adults are shown.