We investigated the hypotheses that symptom progression in Alzheimer's disease is related to onset age and familial aggregation. In a psychiatric outpatient clinic we examined a cohort of 265 consecutively admitted patients 90 of which were diagnosed mild to moderate Alzheimer's disease according to the ICD-10 research criteria. Within twelve months follow-up 73 cases of these 90 patients were investigated twice. We found that early onset cases compared to late onset cases as well as patients with a familial aggregation compared to patients without such an aggregation were no different with respect to the rate of symptom progression in Alzheimer's disease. Furthermore, the hypothesis that early onset cases with a familial aggregation more rapidly deteriorate cognitively compared to late onset cases without such an aggregation could not be confirmed. Our results suggest that the large interindividual variation of symptom progression in Alzheimer's disease cannot be explained by onset age and familial aggregation.