The goal of the study is to examine the cortical activity during speech perception and speech production in idiopathic stutterers compared to fluent speakers. Therefore, the noninvasive method of magnetoencephalography (MEG) is used. A better understanding for the complexity of speech perception and its pathology should be developed. Fundamental properties of stuttering are repetitions, prolongations, and blocks. In most cases stuttering emerges between 2 and 5 years of age. The auditory feedback should become less important during development, as soon as information about mispronounced words does not occur anymore. During speech development this control function should be adopted by other systems. In stutterers the dominance of the acoustic control should remain. Brain imaging studies with positron emission tomography (PET) or magnetic resonance imaging (MRI) show defects in the network of motor system, in the lateralization of speech areas, and functions of the auditory cortex. Magnetoencephalographic studies describe a similar variety as cause of stuttering. There may be defects in the auditory feedback, a modification of the lateralization of speech areas, or an alteration of co-action of motor planning and auditory system. The benefit of magnetoencephalography is a very good temporal resolution in the range of milliseconds combined with good spatial resolution. Therefore, it is well suited to examine the dynamics of cortical processing during stuttering. In this study evoked components of the auditory systems related to complex sounds, vocals, consonant-vocal combinations, and single words are analyzed. Differences of these components in the auditory cortices of stutterers and fluent speakers are hypothesized as well in temporal structure as in localization and lateralization.