Sulfated fucans are among the most abundant sulfated polysaccharides found in marine organisms. These polysaccharides are found in marine invertebrates and also in brown algae. The sulfated fucans from invertebrates are linear polymers, with a regular and repetitive units. In contrast, it is difficult to identify clear repetitive units in the algal fucans due to different types of glycosidic linkages, various sulfation sites and the presence of branches. These complex structures limit the attempts to correlate biological activity of the algal polysaccharides with specific structural features. Recenttly, we described a selective procedure to obtain oligosaccharides from invertebrate sulfated fucans, based on mild acid hydrolysis (Glycobiology, 15(4), 369-81, 2005 and 15(12), 1376-85, 2005). We now extend a similar procedure to the algal fucan. We observed that mild acid hydrolysis of the sulfated fucan from the marine alga Laminaria abyssalis yields oligosaccharides with well-defined molecular size, which can be analyzed by PAGE and fractionated by gel filtration on Bio Gel P10. We test different HCl concentrations, and various temperatures and the time course of the hydrolysis. The more appropriate concentration to obtain a large range of oligosaccharides with well-defined molecular size is 0.01M HCl, at 60^oC for 4 h. The structure of these oligosaccharides can now be analyzed by NMR. Possibly, the oligosaccharides obtained from algal fucan will help to define the structure versus biological activities of this complex polysaccharide.