Organic brain syndrome, also known as senile dementia, is an age-related disease affecting memory, intellect, and communicative function of the elderly. Though the ultimate demise of communicative function in organic brain syndrome patients has been documented, scant data exist as to a) the dissolution of speech and language skills during the disease course, b) differences in communicative function between the senile and normal senescents, and c) the sensitivity of language and speech tests to the presence and extent of organic brain disease. Objectives of this research are to 1) document the nature of language/speech skills in normal senescence, 2) document the demise of language/speech skills in patients with organic brain syndrome, and 3) discover language/speech tests sensitive to the presence and extent of organic brain disease. Four studies have been planned to achieve these objectives. In Study #1 a comparison will be made of the performance of a group of organic brain syndrome patients of a specified etiology to a non-organic brain syndrome group matched for age, socio-economic level, and educational background on tests of cognition, language and speech, and memory/learning. In Study #2 a group of organic brain syndrome patients with specified etiology will be periodically evaluated by means of tests of cognition, language and speech, and memory/learning to assess changes in performance during the disease course. Study #3 has been designed to determine if differences exist in verbal fluency according to task type and presence and degree of organic brain disease. In Study #4 investigation will be made of whether the linguistic abilities to correct phonologically, syntactically, and semantically anomalous sentences and detect lexical, surface structure, and deep structure ambiguities dercreases with age and/or organic brain syndrome.