This dissertation examines ethnic and racial self-identification among the adult children of Iranian immigrants in Southern California. Drawing on 51 in-depth interviews with 1.5 and second-generation Muslim and non-Muslim Iranians, my data suggest that ethnic identity formation among this group is conditioned by powerful influences that are rooted in the often-hostile relations between the United States and Iran. Their experiences illustrate how the word Iranian has taken on a negative connotation because of how Iran is portrayed by the U.S. government, in the media, and in the minds of native-born Americans. In order to deflect the negative stigma associated with their homeland, the majority of 1.5 and second-generation Iranians assert a Persian identity, which emphasizes Iran's pre-Islamic roots and highlights their opposition to the Iranian government. These findings suggest that ongoing antagonistic relations between home and host countries are an understudied, yet significant, factor in the adaptation of second-generation immigrants. Whereas ethnic self-identification is shaped by decades of enduring hostile relations, racial assertions are influenced by generational status, religious affiliation, neighborhood context, and travel to Iran. Non-Muslim Iranians, for example, are more likely to assert a White racial identity, whereas Muslims are more likely to define themselves as "Other." As research on Arab Americans also suggests, the post-September 11th context has made Muslim Americans more conscious of their ethnic, racial, and religious differences with natives.