Twenty elderly chronic schizophrenic inpatients of both sexes, age ranging from 60 to 73 years (mean age 63 +/- 0.81 years), diagnosed according to DSM III-R, were treated with fluphenazine decanoate, 12.5 mg intramuscularly, administered every 21 days for six months. Psychopathological features were assessed by means of the Brief Psychiatric Rating Scale at time 0 and then weekly. At 0, 6, 12, 24, 36, 48, 72h and 7, 14 and 21 days after each administration, extrapyramidal side-effects were evaluated using the Extrapyramidal Side-Effects Scale. Fluphenazine was significantly effective in treating symptoms such as emotional withdrawal, blunted affect, suspiciousness, thought disturbances, but not hallucinations. The most severe extrapyramidal side-effects occurred within the first two days of administration of fluphenazine, with a peak after 36 h, following the first four administrations of the drug, possibly related to early peak plasma concentrations. The severity of these effects was reduced after the fifth injection indicating the occurrence of tolerance mechanisms during long-term fluphenazine administration.