Mild cognitive impairment (MCI) refers to persons who are slightly cognitively impaired for age but do not meet the criteria for dementia. MCI has been related to a pre-dementia stage of Alzheimer's disease (AD). However, other possible diagnoses such as cerebro-vascular disease, frontotemporal dementia or normal aging have been considered. Diagnosis, etiology and conversion to dementia are a source of ambiguity in MCI. The aim was to evaluate the opinion of experts on dementia and of general practitioners concerning MCI. A total of 24 experts from Argentina and Brazil (16 neurologists and 8 psychiatrists) and 30 general practitioners agreed to reply to a questionnaire on MCI (adapted from Dubois inventory, 2003). Of these, 92% of experts considered MCI as an ambiguous entity, not necessarily as a "pre-dementia" stage; 63% confirmed a tendency to worsen over the time and 83% of experts decided to initiate treatment using cholinesterase inhibitors, memantine and vitamin E. The opinion on MCI was that a priori it is not only an Alzheimer disease pre-dementia stage, but most of them consider the treatment against AD. MCI is a heterogeneous entity that should be classified as an open category and making it necessary to standardize definitions and design diagnosis guides to better understand Alzheimer disease pre-dementia stage.