Histological examinations were made of cane toad (Bufo marinus) tadpoles after exposure to freeze-thawed Cylindrospermopsis raciborskii whole cell extracts and live C. raciborskii cultures containing sublethal concentrations of the blue-green algal toxin, cylindrospermopsin (CYN). Toxin exposure resulted in tissue injuries to multiple organs, with particular severity noted in the liver, intestine, nephric ducts and gill epithelia. The extent of cellular damage was similar across trials exposing tadpoles to aqueous and cell-bound toxins, despite unequal toxin concentrations being present in each. It was concluded that the presence of cell-bound toxin, which may be directly ingested via grazing, plays a crucial role in the exertion of histological effects in B. marinus. This work provides baseline information regarding the ecotoxicity of CYN toward amphibians. The range of cellular effects noted in CYN-exposed tadpoles suggests that toxic C. raciborskii blooms could represent considerable health risks to amphibian populations and indicate potentially far-reaching ecological impacts of toxic C. raciborskii blooms.