This study is an examination of the beast motif associated with Stephen Dedalus in Joyce's Ulysses. The motif has its origins in Joyce's earlier novel, A Portrait of the Artist as a Young Man. In Ulysses the beast motif is related to Stephen's feelings of guilt and remorse over his mother's death and includes characterizations of Stephen as a fox, a dog, a rat, and a vampire. The motif consistently carries a negative connotation. Several literary sources for the imagery of the beast motif are apparent in Ulysses, including two plays by John Webster, a poem by Matthew Prior, medieval bestiaries, and a traditional Irish folk riddle. The study of the continuity of the beast motif in Ulysses helps to explain the complex characterization of Stephen Dedalus.