General paresis occurs in senility with considerable frequency. In the State of New York, about 10% of paretics admitted for the first time to state hospitals are 60 years old or more.The incubation of the senile type of paresis is generally either extremely long (40-50 years), or rather short (5-7 years). The diagnosis is often made difficult by the fact that the blood serology is negative, in spite of the progress of the histologic inflammatory process.Pathologic investigations revealed that these cases may be divided into two groups: the first group, by far less common, characterized by intense inflammatory changes, presence of alterations typical of senility, and absence of arteriosclerotic lesions; the second group characterized by milder inflammatory changes, absence of alterations typical of senility, and the almost constant presence of arteriosclerotic lesions.Study of the interrelations between the paretic process, cerebral arteriosclerosis, and senility, seems to indicate that (1) the neuroluetic inflammatory process may have an inhibitory influence upon the neuropathologic changes of senility. On the other hand the senile process may have a stimulating influence upon the neuroluetic inflammation.(2) Neurolues may accelerate the arteriosclerotic process of the brain. Cerebral arteriosclerotic changes in turn may tend to diminish the intensity of the inflammatory process.Abstract Teaser