The possibility of cultivation of the giant kelp Macrocystis pyrifera was successfully experienced in France on the north coast of Brittany. In order to evaluate the possibility of eventual acclimation on the French shore, study tour was undertaken on the Californian and Chilian coasts on main kelp beds. Effects of such beds on general ecology, fish resources, sportfishing, navigation, beach cleanliness, and alginates industry are analyzed. Factors controlling kelp distribution and hazards of wide distribution are discussed. Macrocystis seems to be able of developing and maintaining a large standing crop and to contribute to a large and stable associated fauna. The advantage of enhancing fishing greatly outweight the minor disadvantage of navigational interference. Introduction in France seems desirable if the same beneficial effects could be expected. The possibility of a test experiment on a large scale, under permanent control, is discussed.