The aim of this study was to evaluate the prevalence of rhinitis-related symptoms among children living in different parts of Latin America (LA) considering all centers involved in ISAAC Phase Three (Ph3). 93,851 children (6-7 yr-old) from 35 centers in 14 LA countries and 165,917 adolescents (13-14 yr-old) from 56 centers in 17 LA countries were enrolled. The mean prevalence rate of current rhinoconjunctivitis was 12.7% and ranged from 5.5% in Rosario City (Argentina) to 21.2% in Caracas (Venezuela) for the schoolchildren. The mean prevalence rate of current rhinoconjunctivitis was 18.5% and ranged from 7.1% in Cuernavaca (Mexico) to 45.1% in Asuncion (Paraguay) for the adolescents. These indexes were among the higher observed during ISAAC Ph3. In general the prevalence of rhinitis-related symptoms was higher among the Spanish speaking centers. Environmental risk factors must be evaluated in order to explain the differences observed even in centers from the same country.