Animal and human studies suggest that directional categorization of frequency modulated (FM) tones (rising vs. falling) is a function of the right auditory cortex (AC). To investigate this hemispheric specialization in more detail we analyzed both the binaural and monaural representation of FM tones and the influence of contralateral white noise on the processing of FM tone direction. In two fMRI-experiments FM tones with varied direction, center-frequencies, and duration were presented binaurally or monaurally without contralateral white noise (experiment I) and with contralateral white noise (experiment II) while the subjects had to perform the same directional categorization task. In experiment I contralateral FM tones led to strongest activation, binaural FM tones to intermediate and ipsilateral FM tones to weakest activation in each AC. This is in accordance with binaural response properties of neurons in animal AC. In experiment II contralateral white noise had no significant effect on the activation of left AC by FM tones whereas in right AC it led to a significant increase in activation for ipsilateral FM tones. This result provides further support for the critical role of right AC for directional categorization of FM tones which for ipsilateral input has to be processed in competition to the excitatory input of white noise via the direct contralateral pathway.