Chemorepellents are compounds which cause cells to move away from the source of the repellent, or down a concentration gradient. Chemorepellents are important mediators of neuronal development, guiding axonal growth and direction. In my lab, we use the ciliated protozoans, Tetrahymena thermophila and Paramecium tetraurelia as model systems for chemorepellent signaling. We use a combination of behavioral assays and pharmacological inhibitors to characterize signaling through various repellent receptors. To date, we have characterized a G-protein linked polycation receptor in Tetrahymena, a tyrosine kinase linked receptor in Tetrahymena, and a tyrosine kinase linked receptor in Paramecium. This data helps us understand how chemorepellents work in ciliates, and may be helpful in understanding chemorepellent mechanisms in higher organisms.