SUMMARY This study compared the ability of the closely related plants Ammi majus (L.) and Ammi visnaga (L.) Lam. to induce photosensitization, with goslings as the experimental model. Goslings fed stems, leaves, and flowers of A. visnaga failed to develop clinical symptoms of photosensitization. The same weight of seeds of the two plants fed to goslings caused photosensitization solely in the geese fed A. majus seeds. Only birds both fed A. majus seeds and exposed to sunlight were clinically affected. A brief botanical description of the two plants is given to aid in their identification.