A study in a consecutive series of children aged 10 months and 2 and 4 years, attending for general health examinations, allowed comparison of a group of 94 children with serous otitis with a control group of 85 children. About 100 parameters, including past history, and results of clinical and paraclinical examinations, were compared, and findings used for statistical analysis. Results confirmed the usual clinical picture of serous otitis in children. In addition, four criteria were demonstrated that were all related to an allergic diathesis: a previous history of familial allergy, spasmodic nocturnal cough, blood hypereosinophilia and maxillary rhinosinusitis. Allergy appears, therefore, to play a role in the physiopathology of serous otitis and should be the object of screening with the aim of prevention and therapy.