1 Can a legalization program for immigrants generate conflict among natives? Jesús Clemente Gemma Larramona* Universidad de Zaragoza The aim of this paper is to analyze the effects of a legalization program on the number of illegal immigrants, and on the income of heterogeneous native workers, in a context where skilled and unskilled natives and legal and illegal immigrants co-exist. In an overlapping generations model, we have determined that the effects of the program are not monotonous. More particularly, in certain circumstances, a change in the quota of legalized immigrants may sometimes have contradictory effects on native workers’ income, depending on whether they are skilled or not. Keywords: Illegal immigration; legalization quota; qualification. JEL: F22, J61,J68. * Corresponding author: Gemma Larramona, Departamento de Análisis Económico. Facultad de Ciencias Económicas y Empresariales Gran Vía, 2. 50005 Zaragoza (Spain) Tel. 34 976 76 2789 Fax. 34 976 76 1996 e-mail: gemmalar@unizar.es Acknowledgements We thank Josefina Cabeza, Rosa Aísa and Fernando Pueyo for their helpful suggestions and thoughtful comments on the model and the calibration.