The capacity of two species of edible seaweeds (Wakame, Undaria pinnatifida and Chondrus, Chondrus crispus) to modify the rate of white bread starch digestibility by an in vitro digestion system, as well as glucose retardation index and apparent viscosity were studied. Both Algae showed different effect on glucose retardation index. While Wakame did not make difficult dialysis of glucose, it only retained 2.50 +/- 2.99% to respect a negative control. Chondrus impaired the diffusion of a 28.70 +/- 2.35% of glucose, which are very close to those of citrus pectin (31.50 +/- 4.12%). On the other hand, viscosity of Chondrus solution was higher than Wakame and slightly lower than citrus pectin solution. The analysis showed a very low content of total starch in Wakame (0.51%) and Chondrus (0.47%). Algae reduced the digestion of white bread starch. The profile of starch hydrolysis was characteristic for each alga. Glycaemic index estimated from the degree of starch hydrolysis within 90 min was low (79) with respect to white bread (value 100). Seaweeds showed a suitable capacity to modify in vitro starch digestibility of white bread. Chondrus produces a more pronounced response. This fact seem to be due to different composition of samples.