The cognitive and behavioral effects and the safety of oxiracetam therapy during a placebo-controlled trial and the relevant follow-up up to 1 year in patients with senile dementia of Alzheimer type (SDAT) and multi-infarct dementia (MID) of mild to moderate degree were studied. Sixty male and female outpatients participated in the double-blind, placebo-controlled, parallel-group, randomized trial, comparing the effects of oxiracetam 800 mg b.i.d. and placebo during 90 days of treatment. At the end of therapy, statistical analysis evidenced significant improvements in the group receiving oxiracetam in respect to the placebo group on Mini Mental State Examination, Auditory Continuous Performance Test, Rey’s 15 Words Test, Block Tapping Test, Mattis Word Fluency, Luria Alternating Series and Instrumental Activities of Daily Living. Afterwards, 29 of the 30 patients who received oxiracetam, participated in the open follow-up study, receiving 800 mg b.i.d. oxiracetam for a total standard period of 1 year. Statistical improvements in comparison to baseline were again found on the same tests of the first 90 days (except for Rey’s 15 Words Test) and on the Memory item of the Inventory of Psychic and Somatic Complaints Elderly. During the late phase of the follow-up, statistically significant worsenings in comparison to baseline were observed on Digit Span Backward, Gibson’s Spiral and some non-memory items of IPSC-E. Neither severe adverse events were observed during the whole study, nor changes in routine laboratory examinations. In conclusion, in the present population of patients with mild to moderate degree dementia, the safety of 1,600 mg/day of oxiracetam also up to 1 year of treatment was confirmed. Clinical efficacy was also confirmed, although some improvements seen after the first months were not completely maintained after 12 months.