The objective of our study was to review retrospectively the clinical, radiological and therapeutic findings in 62 adults with acute mastoiditis treated at the ENT Department of Ferrara from 1992 to 2010. 62 adult cases fulfilled the following inclusion criteria: otoscopical evidence of co-existent or recent otitis media; postauricular swelling, erythema or tenderness; protrusion of the auricle; fever and/or significant radiological findings of mastoiditis. Conservative treatment comprehended antibiotic ± ventilation tube. Surgical procedures comprehended mastoidectomy or mastoido-tympanoplasty. The incidence of adult's mastoiditis in our district (0.99 cases/year/100.000 inhabitants) has maintained quite stable during the considered 19-year period. The typical clinical presentation was observed in 48% of cases. Complications were meningitis (15 cases), meningo-encephalitis (1), meningitis associated with lateral sinus thrombosis (1), facial nerve paralysis (11), and labyrinthitis (8). In all cases except one, the facial palsy recovered completely and no mortality was observed due to these complications. Complete cure was obtained with conservative treatment in 69% of uncomplicated cases and in 24% of patients with intracranial complications. Mastoiditis in adults may present as the acute classical form, as well as latent forms which often have prolonged and insidious development followed by a rapid clinical deterioration. Clinical features are frequently atypical, while incidence of meningitis and other complications is still high particularly in the most elderly. Thus, great care is required from clinicians to make an early diagnosis in order to promote adequate treatment.