An in vivo and an in vitro toxicity test method is described using an organism or part of an organism from the class Gastropoda. The method is particularly useful for toxicity testing of chemical substances intended for application to human or animal mucosa, such as the intestinal, vaginal, buccal, nasal or respiratory mucosa. The test method may be used both as a screening test and also as a quantitative toxicity test suitable for ranking the toxicity of chemical substances.