To investigate the longitudinal changes in age at onset and the initial symptom of patients with sporadic amyotrophic lateral sclerosis (ALS), we performed a single hospital-based retrospective study over the past 38 years. A total of 280 sporadic ALS patients (169 men and 111 women) hospitalized in our department between 1965 and 2003 were investigated in this study. The clinical features including age at onset and the initial symptom of these patients were obtained from medical records. All the patients underwent an intensive diagnostic evaluation including electrophysiological examination, laboratory examinations of blood and cerebrospinal fluid, and neuroimagings of the brain and spinal cord to exclude other conditions similar to ALS. The mean age at onset was 58.3 +/- 11.3 years and age at onset significantly increased at the rate of 0.459 years per year (r = 0.406, p< 0.001). The percentage of patients whose age at onset was > or = 70 years has increased from 3.0% (1980-1984) to 31.1% (2000-2003). To investigate the initial symptom of senile-onset ALS, patients whose age at onset was > or = 70 years were analyzed. The percentages of bulbar palsy-onset patients with onset in terms of age were 62.5% (30/48 patients; > or = 70 years) and 23.3% (54/232 patients; <70 years). The odd ratio for bulbar palsy was 5.40 (95% confidence interval, 2.79-10.44). Taken together, our study demonstrates that the ratio of senile-onset ALS has significantly increased, and that there were more bulbar palsy-onset patients among the patients.