In this study, we examined the relationship between within-person blood pressure and cognitive functioning. We conducted an analysis on 36 community-dwelling elderly individuals (age range = 60-87 years). Participants measured their blood pressure and completed cognitive tasks (i.e., the Rey Auditory Verbal Learning Task, the Letter Series test, and the Number Comparison test) twice a day over 60 consecutive days. We observed a significant interaction between within-person change in blood pressure and average blood pressure for the Letter Series test. Individuals with high blood pressure tended to perform poorly, particularly on occasions when their blood pressure level was above their personal average. These results demonstrate that the relationship between blood pressure and cognition at the between-person level and the relationship within each individual should be further explored simultaneously.