Cyanobcateria blooms represent a major global concern due to certain toxin-producing species. These toxins are classifies into 3 groips bases on the mode of action: neurotoxins, dermatotoxins and hepatotoxins. Microcystins belonging on the group of hepatotoxins are the most studied, the most dangerous and the most encountered in waterways. It is in this context that we proposed to evaluate the microcystin content specifically LA which is as dangerous as the LR analogue. Monthly monitoring from june to september 2021 allowed us to collect water samples from three surface waters in Ivory Coast (Aghien Laoon, Adzopé Water Reservoir and Angboville Seuil). Microscopic observations made it possible to identify different cyanobacteria, and the determination of microcystin LA (MC-LA) present in the water samples was carried out by HPLC/UV. The results revealed the presence of fifteen (15) genera of cyanobacteria in the three water bodies studied including four (4) potentially producing microcystin. Oscillatoria sp was the most represented with a frequency àf 100% followed by genera Aphanocapsa, Calothrix, Chroococcus, Cylindrospermopsis Merismopedia, Microcystis, and Planktothrix (66,66%). The genera Anabaena, Anabaenopsis, Lyngbya, Phormidium, Pseudanabaena, Snowella and Synechococcus were the least represented (33.33%). The variant LA was identified on the Aghien lagoon and measured at different concentrations, the maximum and minimum values of which were respectively 3.5 µg/L at station 4 and 0.68 µg/L at station 1.