Karenia mikimotoi (Miyake et Kominami ex Oda) G. Hansen et Moestrup is a harmful dinoflagellate and forms massive blooms in coastal waters of the temperate regions in Europe and East Asia, typically in the west Japan. Blooms of this species sometime cause massive mortality of fish and invertebrates, thereby resulting in enormous fisheries damage. Fish killing mechanisms of K. mikimotoi have been extensively studied so far however the significant causative agents for massive mortality of marine organisms have not been enough understood. Recent studies demonstrated that algal toxins like polyether and purine alkaroide toxins are produced by polyketide synthases (PKSs) and 'sxt' genes, respectively. So far, completed PKS or 'sxt' genes in several microalgae have been characterized, but never K. mikimotoi. Information on the toxin-related genes of microalgae is rapidly accumulated recently. As for K. mikimotoi, despite an important harmful species in fisheries, there are little sequence data accessible to understand the toxicity. In this project, we aimed to construct an RNA-sequence library for K. mikimotoi for further researches on dinoflagellate studies in all aspects including toxic substances.