The processing of the German plural has been examined in a range of behavioral and neurophysiological studies. A number of studies so far showed differences between the processing of the default plural form -s and the irregular plural form -(e)n. While previous studies focused on the examination of generally two plural categories (e.g. -(e)n versus -s), the current study aimed at examining four German plural categories with different morpheme endings and violating them cross-wise. The results of the current auditory event-related (ERP) and reaction time study show general similarities between the more acoustically salient plural categories. In the early latency range from 200 - 400 ms -n violated by -s plural (and the cross-condition) act differently from the -e versus -er plural violations (and the cross-conditions) but in the later time windows only violation effects are visible. Processing differences may be explained by the morphological characteristics of the plural categories and/or phonetic differences between the suffixes.