Harmful algal blooms in the past three decades appear to have grown in incidence, intensity and geographical distribution with negative impacts on public health and economy values. Each year the algal biotoxins are responsible for more than 60.000 intoxications with an associated mortality rate of 1.5%. The present review summarizes current knowledge and perspectives on marine and freshwater algal toxins with an emphasis on different genus of algae capable to produce toxins and their physiology. The typologies of toxins, their chemical structure and mechanisms of action, the factors that stimulate their biosynthesis and the current techniques used for algal toxins removal will be also reviewed.