We would like to emphasize that the goal of this study is to evaluate the efficacy, tolerability and safety of memantine hydrochloride in enhancing the cognitive abilities of young adults with Down syndrome aged 18-32 years. Therefore, the present investigation is a non-overlapping and complementary clinical trial to the randomized, placebo-controlled clinical trial on the efficacy and tolerability of memantine in preventing age-related cognitive deterioration and dementia in people with Down syndrome age 40 and over (http://www.clinicaltrials.gov/ct2/show/record/NCT00240760?term=down+syndrome&rank=15) currently being carried out by our colleagues in London.