We have studied the relationship between the apolipoprotein E gene (APOE) and the development of myoclonus, tremors, rigidity and seizures in 168 patients with probable early-onset Alzheimer's disease (AD). There was a statistically significantly lower risk of tremor for carriers of the epsilon 4 allele of APOE. This allele was also associated with an increased risk of myoclonus. Our findings suggest that there may be differences in progression and clinical appearance in early-onset AD related to the APOE genotype.