Lateralization of verbal processing is frequently studied with the dichotic listening technique, yielding a so called right ear advantage (REA) to consonant-vowel (CV) syllables. However, little is known about how background noise affects the REA. To address this issue, we presented CV-syllables either in silence or with traffic background noise vs. "babble". Both "babble" and traffic noise resulted in a smaller REA compared to the silent condition. The traffic noise, moreover, had a significantly greater negative effect on the REA than the "babble", caused both by a decreased right ear response as well as an increased left ear response. The results are discussed in terms of alertness and attentional factors. (Contains 2 figures.)