Prospective memory is a complex cognitive function requested to remember a planned action. For example, this function is particularly important in elderly people to remember taking medication at the appropriate time. Two key objectives were pursued in an interindividual differences approach. The first goal was to have a better understanding of prospective memory in aging people. Thus, we wanted to identify the cognitive mechanisms underlying the age-related decline in laboratory and naturalistic prospective memory tasks. The second goal was to estimate how prospective memory can be improved in elderly people. To that end, we performed four studies using samples of aging people. The results of the two first studies indicated that retrospective memory and executive control processes mediate the relation between age and prospective memory. In the third study, the results showed that elderly people compensated spontaneously some of their prospective memory problems using external memory aids. These studies allowed us to develop and to test a cognitive intervention program based on the reinforcement of retrospective memory, executive control processes, and metacognitive knowledge. The results indicated any effect of the intervention program on prospective memory performance. These suggest that individualized cognitive interventions focused on specific prospective memory problems would be more suitable than interventions designed to improve the global functioning of prospective memory in elderly people