The objective of our study was to examine the relationship between the presence of the apolipoprotein E (apo E) epsilon 4 allele, psychiatric symptoms, and extrapyramidal signs (EPS) in probable Alzheimer's disease (AD). The apo E epsilon 4 allele modifies the risk and age at onset of AD. However, it still needs to be determined whether it is a marker for specific clinical subgroups. The frequency of clinical signs and symptoms was examined in 194 AD patients with the apo E epsilon 3/3 (N = 79), epsilon 3/4 (N = 96), and epsilon 4/4 (N = 19) genotypes participating in a longitudinal study of dementia. Each patient was assessed with semistructured psychiatric and neurologic examinations. Patients with the epsilon 4/4 genotype had an earlier age at onset of dementia (p = 0.03). However, no individual psychiatric symptom or neurologic sign was associated with the presence of the apo E epsilon 4 allele, including major depression (odds ratio [OR], 1.14; CI, 0.50 to 2.45; p = 0.78), psychosis (e.g., delusions and hallucinations) (OR, 0.66, CI, 0.35 to 1.25; p = 0.20), and EPS (in neuroleptic-free patients) (OR, 0.82, CI, 0.45 to 1.49; p = 0.52), after controlling by age at onset, duration of the symptoms, education, and severity of dementia. The presence of the apo E epsilon 4 allele has limited utility in the characterization of neurologic and psychiatric subgroups in probable AD patients. The apo E epsilon 4/4 genotype appears to be related to age at onset of AD, consistent with previous findings.