This chapter reviews the toxicology of seafood toxins, and highlights the deficiencies in the toxicological data that preclude proper risk assessment of such substances. Risk is a function of the dose of the substance and its intrinsic toxicity. Two scenarios of toxic effects may be envisioned. Firstly, there are acute effects, induced by a single exposure to a toxic compound. Secondly, there are chronic effects, induced by repeated exposure to a toxic compound. The toxicological information on azaspiracids (AZA) is inadequate. After oral administration to mice, AZA-1 was detected in the heart, lungs, liver, spleen, kidneys, brain, and gastrointestinal tract of the animals. The Economic Co-operation and Development recommends that gavage should be used in chronic toxicity studies only when this route and method of administration represents potential human exposure, as with pharmaceuticals. Sex, strain, and age have been shown to influence susceptibility in acute toxicity studies.