The aim of the present study was to analyze the ApoE4 allele frequency in interaction with CSF concentrations of Aβ42, t-tau and p-tau in a large heterogeneous sample of MCI patients followed longitudinally with different progression outcomes: MCI-stable, MCI-AD converters and MCI progressing to other forms of dementias. The gene discussed is APOE; the disease is Alzheimer disease.