The marine brown alp Striaria attenuata has a bipolar distribution. It is known from temperate coasts on both sides of the North Atlantic, Japan, Southern Australia, Tasmania, and New Zealand. In the present paper, recent findings of the alga in temperate South America are reported, thus extending the geographical distribution of the species. In addition, the life history of individuals from Argentina and Chile was studied in laboratory culture. A specimen from southern Chile (Chiloe Island, 43-degrees-S) showed alternation of macroscopic sporophytes with dioecious microscopic gametophytes that formed isogametes in multiseriate plurilocular gametangia. In contrast, a plant from Argentina (northern Patagonia, 41-degrees-S) had a direct life history, never forming plurilocular zoidangia. Thus, two different life histories exist in South American Striaria attenuata. They are compared with reproductive patterns in European isolates of the same species.