There is interest in the paradigm that relates environmental sea changes to the emergence of diseases that affect both aquatic organisms in the sea and human beings. The emergence of Vibrio parahaemolyticus as an important cause of epidemic summer diarrhea in 2004 and 2005, confined mainly to the tenth region in Chile, could be a manifestation of this trend. This and other areas of the country have also experienced several outbreaks of paralytic shellfish poisoning (PSP), diarrheal shellfish poisoning (DSP) and amnesic shellfish poisoning (ASP) caused by harmful algal blooms (HAB) of Alexandrium catenella, Dinophysis acuta and Pseudonitzchia species, respectively. The short historical record of these pathological phenomena in Chile suggests that they are increasing in frequency and expanding their geographical range. The V parahaemolyticus isolates responsible for the Chilean outbreaks correspond mainly to the pandemic strain O3:K6. HAB found in Chile and the intoxications caused by them have similar biological characteristics to those described in other areas of the world. The tenth region, the area where these problems are emerging, produces approximately 80-90% of the shellfish consumed in Chile and a large proportion of the shellfish that is exported. Prevention of these public health problems can be attained by developing policies that increase environmental surveillance for Vibrios and toxic algae, improve the epidemiological surveillance of acute diarrhea and algal intoxications after the ingestion of raw bivalves, and educate the population on the mode of transmission of these diseases. Scientific capacity and laboratories need to be developed to widen the limited knowledge of the biology of Vibrio and toxic algae and the environmental factors that favor their emergence as public health and economic problems in Chile.