ABSTRACT: Toxic cyanobacteria occur in Greek surface water bodies. However, studies on the occurrence of cyanotoxins (CTs) are often limited to mainly microcystins (MCs), with use of screening methods, such as ELISA, that are not conclusive of the chemical structure of the CT variants and can be subject to false positive results. A multi-lake survey in Greece (14 lakes) was conducted in water and biomass, targeted to a wide range of multi-class CTs including MCs, nodularin-R (NOD), cylindrospermopsin (CYN), anatoxin-a (ANA-a) and saxitoxins (STXs), using multi-class/variant LC-MS/MS analytical workflows, achieving sensitive detection, definitive identification and accurate quantitation. A wide variety of CTs (CYN, ANA-a, STX, neoSTX, dmMC-RR, MC-RR, MC-YR, MC-HtyR, dm3MC-LR, MC-LR, MC-HilR, MC-WR, M
