The study aimed to characterize neuropsychiatric symptomatology in Alzheimer's disease (AD) and investigate the role of APOE genotype and other clinical variables in the onset of neuropsychiatric disorders. Moreover, an attempt to study the evolution of behavioral and psychiatric symptoms was made. Fifty-three consecutive outpatients with AD were enrolled. Twenty-four were followed longitudinally for 1 year. MMSE was used to evaluate cognitive functions. The neuropsychiatric inventory (NPI) was administered to assess behavioral and psychiatric symptoms. Genotyping was determined through laboratory testing. At baseline, no specific neuropsychiatric disorder was significantly associated with ApoE genotype, but associated with a peculiar neuropsychiatric profile. Patients with epsilon(4) allele showed a wider range of neuropsychiatric disturbances when compared to non-carriers and higher scores for hallucinations and aberrant motor behaviors. The longitudinal results suggest different trends in both groups: over time, epsilon(4) carriers showed an increase/delayed onset in some symptoms and a parallel decrease in others, while non-carriers presented an undifferentiated worsening of symptomatology. Clear relations with other clinical and demographic variables were also found. APOE epsilon(4) allele is associated to a peculiar neuropsychiatric profile characterizing the onset and evolution of Alzheimer's disease.