The objective was to investigate the familial occurrence of the neurodegenerative condition amyotrophic lateral sclerosis (ALS), Parkinson's disease and dementia in the relatives of Irish ALS patients. A retrospective case control chart review study was conducted to extract the neurological family histories of Irish ALS patients and controls who attended the National Neurological Centre between January 2001 and January 2006. In total, details were extracted from 197 ALS and 235 general neurology pedigrees. Using the recurrence risk, lambda, ALS (lambda (1st degree)=7.77), Parkinson's disease (lambda (1st degree)=2.67) and dementia (lambda (1st degree)=6.21) were reported more frequently in relatives of ALS patients compared to those of non-ALS controls. Within sporadic ALS kindreds, the presence of neurodegenerative disease was not uniformly distributed. This study supports the conjecture that neurodegenerative disease aggregates within ALS kindreds, and indicates a shared genetic susceptibility towards some neurodegenerative phenotypes.