Word association data were obtained from two cohorts of British adults. Young adults (aged 21–30 yrs) and older adults (aged 66–81 yrs) responded to 90 words in a discrete word association task. An associative frequency measure was calculated by counting how many participants produced a particular word and then converting this number into a proportion. The degree of overlap between the cohorts in terms of dominant responses, the responses with the highest association frequencies, was moderate. Dominant responses were common to the two cohorts for only 36 of the 90 items. When the top three responses were considered the degree of overlap increased to approximately 60{\%}. Four measures of response heterogeneity were calculated for each stimulus item. Comparison of the responses of the younger and older adults indicates that there was less response heterogeneity amongst the older cohort. These norms should be of use to investigators interested in developmental changes in the structure of semantic memory across the adult lifespan as well as to researchers interested in comparing results from neurologically impaired older adults to a normative sample from the same age cohort.