The aim of the present research was to study the effects of age on the adherence and chemotaxis capacities of macrophages. Macrophages were obtained from the peritoneum of young and old mice (young, 12 +/- 4 weeks; old, 68 +/- 6 weeks) and young and mature guinea pigs (young, 12 +/- 1 weeks; mature, 108 +/- 2 weeks). Adherence of macrophages was evaluated with a plastic adherence technique, and chemotaxis in a Boyden chamber. The macrophages from old animals showed a higher adherence capacity (studied at 10, 40 and 60 min of incubation), and lower chemotaxis capacity in both mice and guinea pigs. The effect of physical activity stress (swimming until exhaustion) was also studied, both with and without a previous training program, on the adherence and chemotaxis of macrophages from young and old mice. While the physical activity stress (detected by the increase of the serum corticosterone concentration) did not induce changes in adherence or chemotaxis of peritoneal macrophages from young mice, in the old mice, there was a decrease in adherence and an increase in chemotaxis.