A 40-year-old HIV-positive right handed homosexual man was admitted for progressive mental deterioration coexisting with permanent segmental middle-amplitude arrhythmic, asynchronous and asymmetrical myoclonic jerks. EEG showed fronto-central bursts of rhythmic triphasic 1.5-2 Hz sharp waves similar to the characteristic periodic pattern of Jakob-Creutzfeldt disease. Biological procedures were negative, thus eliminating a metabolic encephalopathy. Dramatic neurological improvement occurred shortly after initiation of i.v. and then oral zidovudine which produced perfect EEG normalisation. This unusual electroclinical presentation of the AIDS-dementia complex underlines the fact that this affection may present a diagnostic challenge, particularly in individuals in whom HIV infection is unknown.