A progressive sensorineural hearing loss in childhood, with an extremely variable prevalence (from 4% to 30%), has been reported in the literature. This wide range of reported figures could depend on the different criteria used for identifying the deterioration, the groups, and the examined age ranges. The most frequent etiology of progressive sensorineural hearing loss in childhood includes hereditary causes, both syndromic and nonsyndromic, and developmental and infectious causes, whereas metabolic, toxic, autoimmune, traumatic, and vascular etiologies are less common; however, the origin of the hearing impairment often remains unknown. The population for this study consisted of 178 children with bilateral sensorineural hearing loss who were examined between 1971 and 1993 using audiologic tests. Syndromal genetic hearing loss was excluded from the study. A progressive loss of acuity was found in 11 subjects, with a prevalence of 6.2%. The etiology was hereditary deafness in five patients, congenital infection in one, and congenital inner ear anomaly in another patient; in the last four children the etiology was unknown. Onset of deterioration was after 4 years of age in 73% of the patients. The progressive evolution was binaural in almost all patients (10 of 11) and asymmetric in most, with a tendency to a greater deterioration at the frequencies initially least affected.