Actinomycosis is a chronic, suppurative and granulomatous bacterial infection, which tends to form abscesses. Involvement of the central nervous system (CNS) is rare. We describe the clinical and neuroradiological findings of four patients (3 men and one female) diagnosed of actinomycotic brain abscesses. Risk factors were dental pathology, intrauterine device use, alcohol abuse and Rendu-Osler-Weber disease. Clinical manifestations were those of a space-occupying lesion. CT scan findings were varied and little specific: hemispheric or periventricular location, pyocephalus, rim-enhancing and edema. MRI was superior in disclosing pyocephalus. Diagnosis was performed by microbiological and pathological findings. Despite surgery and antibiotics, two of the patients died. In conclusion, the infection of the CNS by Actinomyces is potentially fatal and should be considered in those patients with cerebral abscess.