The relation between knowledge about memory capacity, delayed recall on a 15-word-list task, and sociological lifestyle variables was examined in a sample of 1,398 adults ranging in age between 25 and 82. Participants were sampled from a registration network of family medical practices representing the general population of the south of The Netherlands. Participants were stratified for age, sex, and level of occupational achievement. We found that lifestyle opportunity structure as indicated by social network characteristics and lifestyle conduct as indicated by activity scores were related positively to the dependent variables of memory knowledge and delayed recall. Study results showed that participants with better delayed recall scores had larger social networks, were younger, were more frequently female, had more years of education, and were less externally oriented. Participants with higher metamemory capacity scores had more frequent contacts in their social network, considered themselves more frequently an active person, were younger, were female, reported fewer health complaints, and had a higher internal locus of control. Delayed recall scores did not predict metamemory capacity scores after we controlled for other variables. The results support the conclusion that cognitive performance is influenced significantly by lifestyle components.