Native speakers of Egyptian Arabic make errors in their pronunciation of English that cannot always be accounted for by a contrastive analysis of Egyptian analysis of Egyptain Arabic and English. This study focuses on three types of errors in the pronunciation of voiced and voiceless "th" made by fluent speakers of English. These errors were noted during informal conversations. While not all of the errors can be explained by the surface structure of the native language phonemes, they all fit into a unified system which can be described. The unified system implies that the behaviors are governed by the way in which the deep structure of the native language phonemes act in relation to the target language. (Author/AMH)