The influence of seven highly prevalent somatic chronic diseases on changes in cognitive functioning is investigated in older persons in a prospective design covering a 6-year follow-up period. The data were collected as part of the Longitudinal Aging Study Amsterdam (LASA). The associations between chronic diseases and cognitive functioning during 6 years of follow-up were analyzed among 1358 respondents (age 62-85) using generalized estimated equations (GEE). Cognitive tests were used to assess: general cognitive functioning, fluid intelligence, information processing speed and memory performance. In the fully adjusted models diabetes mellitus, stroke and peripheral artherosclerosis were associated with cognitive decline during a 6-year follow-up period in older persons. In the unadjusted models cardiac disease was negatively associated with memory function. However, after the correction for possible confounders this association became positive. Cancer was also associated with better memory function. A faster decline in especially memory function was found for diabetes mellitus, stroke, cancer, and peripheral artherosclerosis. The study shows that in older persons specific chronic diseases (diabetes mellitus, stroke, cancer, and peripheral artherosclerosis) are associated with decline in one or more domains of cognitive functioning during a 6-year follow-up period. These findings further stress that careful clinical evaluation of cognitive functioning in older persons with these diseases is required in order to provide adequate care.