In embryonic development, many cells migrate in order to correctly form new structures. One way that guidance of this migration occurs is via a repulsion mechanism involving the Eph family of receptors. Signaling through these receptors activates the repulsive mechanism that limits which tissues can interact with each other. The repulsion mechanism is not well understood, but involves the reorganization of the actin cytoskeleton and a loss of cell-cell adhesion. Activation of the EphA4 signaling pathway in Xenopus laevis embryos has been shown to cause the repulsion mechanism. the Rho family of GTPases consisting of Cdc42, Rho, and Rac, has been linked to the reorganization of the actin cytoskeleton and Rho has been demonstrated to be part of the EphA4 pathway. The hypothesis to be tested in this study is that activation of Rac is also part of the EphA4 pathway. To test this hypothesis, mutant Rac RNA coding for constitutively active Rac (caRac) was injected into Xenopus laevis embryos to determine if Rac activation can mimic EphA4 signaling. As the concentration of RNA coding for caRac increased, the degree of cellular dissociation also increased. While further experimentation must be doe to make a conclusive determination, it is possible that the activation of Rac is a part of EphA4 signaling.