The purpose of this study was to determine the prevalence of allergic diseases in the school population of the province of Cádiz in order to confirm the hypothesis that these diseases are more frequent there than in the rest of the Spanish provinces. Four cities of our province were chosen (Ubrique, San Fernando, Algeciras and Medina Sidonia, whose initials form the acrostic USFAM) with clear differential characteristics (climatological, orographical, environmental, etc). In each city, schools, both public and private, were chosen at random. Complete classes were used, and the age-limit was that established in each school. A questionnaire was given to all of the parents who, together with the teachers, were given instructions for its completion. Of the 4,000 questionnaires distributed, 2,572 were correctly completed. Of these, 1,988 answered that their child was non-allergic and 584 as allergic (22.7%). The ratio male/female was almost 2/1 (64.4%/35.6%) and the largest prevalence of these allergic diseases was in the group of children between 10 and 13 years of age. We have found that the prevalence of this pathology in the province of Cádiz is higher than the national mean.