As part of a long-range study on mental functioning in old age, 53 twins (mean age 84 years) were given the Kent-Rosanoff Word Association test, a test which measures the cognitive ability to give discrete verbal association to common stimulus words. In general, the results obtained with the aging twins were similar to those previously reported for young adults tested in the early 20th century, nearly 90% of the responses being found in the 1910 Kent-Rosanoff norm tables. Our results are consistent with the trend reported in the literature toward diminished primary responses with advancing age. Unlike reports in the literature, however, the present study detected no sex differences, possibly due to the small sample size (18 men and 35 women). Moreover, Kent-Rosanoff performance was not significantly related to organic brain syndrome, as measured by psychiatric evaluation, Graham-Kendall Memory-for-Designs test, and Stroop-Color-Word test, possibly because most of the twins were diagnosed as having only a “mild” or “moderate” degree of impairment. The intraclass correlations were higher for MZ than DZ twin partners, the differences reaching statistical significance for two scoring categories, primary and unusual responses. Even though the sample was small, only six DZ and 12 MZ pairs, this finding suggests a possible hereditary component in the verbal associative behavior of octogenarians.