This chapter provides an overview of the individual types of cyanobacterial toxins, focuses on toxins that have been confirmed to, or suggested to have implications for human health, namely, microcystins, cylindrospermopsins, anatoxins, saxitoxins, anatoxin-a(S) and dermatotoxins, the latter primarily produced by marine cyanobacteria. The cyclic peptides microcystins and nodularins are frequently found in fresh and brackish waters, and the acute and chronic toxicity of some of them is pronounced. WHO has established provisional guideline values for microcystin-LR in drinking-water and water for recreational use but recommends that these values may be used for the sum of all microcystins in a sample. For deriving the provisional lifetime drinking-water guideline value (GV), the fraction of exposure allocated to drinking-water was 80% because drinking-water is expected to be the most likely long-term source of exposure. For deriving the provisional short-term drinking-water GV, the default allocation factor for short-term values of 100% was selected, considering that drinking-water is usually the most likely exposure source.