Abstract: In 1969, economist Thomas Schelling introduced a landmark model of racial segregation in which individuals choose residences based on the racial composition of the corresponding neighborhoods.  Simple simulations of Schelling's model suggest this local behavior can cause segregation even for racially tolerant individuals.  In this talk, we provide rigorous analyses of the degree of segregation in Schelling's model on one-dimensional and two-dimensional lattices.  We see that if agents refuse to live in neighborhood in which their type constitutes a strict minority, then the outcome is nearly integrated: the average size of an ethnically-homogenous region is independent of the size of the society and only polynomial in the size of the neighborhood.  A natural question arises regarding how tolerance impacts segregation.  We show the surprising result that tolerance can actually increase segregation: the average size of an ethnically-homogenous region is now exponential in the size of the neighborhood.