A population based study on senile cataracts was conducted on 295 participants in an ophthalmologic examination in a rural area of Ishikawa prefecture. Subjects were above 40 years of age and received an ophthalmologic examination and were personally interviewed. The following results were obtained. 1) Prevalence of senile cataracts increased with age. 2) For eyes with lens opacity grade III 66.3% showed a visual acuity below 0.7, while about 45% with lens opacity grade I or II was a visual acuity below 0.7. 3) Among those determined to have senile cataracts by this study the proportion with a prior diagnosis of senile cataracts was low, i.e., 36% even in advanced cataracts with lens opacity grade III. The proportion improved with worsened visual acuity and having a personal ophthalmologist. 4) Of those already diagnosed with senile cataracts, 56.7% failed to visit an eye specialist after than. This proportion tended to be lower in persons with worsened visual acuity. 5) About a half of those who continued to visit an eye doctor utilized anti-cataract medication. 6) The level of knowledge regarding senile cataracts was statistically lower with age.