Selective attention processes (N2 and P3 components of event-related potentials (ERPs)) have been shown to be impaired in depressed patients but findings have been mixed. Part of this variability might be explained by neurobiological factors. ERPs (Go/Nogo paradigm) were investigated in patients with remitted major depression in relation to S100B. S100B, an astroglial protein with neuroplastic properties, has been shown to be increased in depression. Its pathophysiologic role in depression, however, is not yet sufficiently understood. Patients with increased S100B serum levels (n=6) showed a normal N2- and P3-amplitude in contrast to a reduced N2- and P3-amplitude in patients with normal S100B serum levels (n=6). These findings provide evidence of a correlation between S100B levels and attentional processes in patients with recurrent depression and further substantiate S100B's role as a marker in the course of affective disorders.