Toxic algal blooms began to have significant impacts on developing-country aquaculture in the 1970s, including toxic shellfish and mass mortalities of fish and shrimp. Based on the experiences of developed countries, the potential exists in the waters of developing countries for a wide range of presently unrecorded toxins as well as other effects ofalgal blooms. The implications of these hazards are discussed. Their economic impact, which extends beyond the aquatic sector, is also discussed. Management measures used in both developed and developing countries at the industry as well as the government level are described and assessed. Finally, evidence of a relationship between red tides and aquaculture is discussed.