This document deals with outbreaks of certain human diseases associated with human exposure to compounds produced by algae. Predators feeding on the algae become contaminated by these compounds which, in this way, enter the human food chain. Diseases such as paralytic shellfish poisoning (PSP), ciguatera, and the more recently identified syndromes, neurotoxic shellfish poisoning (NSP) and diarrhoeic shellfish poisoning (DSP), are discussed in the document as well as the evidence of their association with dinoflagellate toxins present in human food. Tetrodotoxin intoxication (putterfish poisoning) is discussed because the compound, which is produced by certain fish in various areas of the world, has a similar action to that of saxitoxin, one of the main components causing PSP. Direct dermal contact with toxins ' from a marine cyanophyte causes a particular type of acute dermatitis, observed in certain areas of the world. No human disease has been identified as being a result of exposure to toxins from freshwater cyanophytes. However, this topic has been included in the review for completeness.