A monoclonal and two polyclonal antibodies to human involucrin were used to look for involucrin epitopes in other species. All antibodies react strongly with the same proteins of monkey, and both polyclonal antibodies react with specific proteins of cow and dog. One of the polyclonal antibodies also reacts with proteins of sheep, guinea pig, rat, and finback whale. The immunoreactive proteins from cow and dog could be purified using a procedure developed for human involucrin. The reaction with the purified dog protein could be blocked by purified human involucrin. The results suggest that involucrin-like proteins have a wider species distribution than originally appreciated.