The cyanobacteria or blue-green algae are natural inhabitants of water bodies. The eutrophication due to anthropogenic pressure favors the massive development of strains of cyanobacteria, some of which are potentially toxic. The main goal of this work was to demonstrate for the first time in Ivory Coast the presence of toxicity gene of cyanobacteria from cyanobacteria culture. Water used by the population for their different needed were sampled in different cities of the country. Several genera known for their ability to produce toxic were highlighted including Microcystis, anabeana, oscillatoria, plancktothrix. Oscillatoria was the most isolated genus with 93% of presence in the samples. The pcr has allowed us to confirm the existence of the gene mcy encoding microcystin in Microcystis. PCR identified the mcygène of microcystis in all the sample (100%) while microcystis was found only 86% by microscopy. The contribution of chromatographic and ELISA techniques will ultimately confirm their toxin production or not.