This study addresses the supralexical inferential processes underlying wellformedness judgements and latencies for a specic sublexical unit that appears in Dutch compounds, the interfix. Production studies have shown that the selection of interfixes in novel Dutch compounds and the speed of
this selection is primarily determined by the distribution of interfixes in existing compounds that share the left constituent with the target compound, i.e. the ‘‘left constituent family’’. In this paper, we consider the question whether constituent families also affect wellformedness decisions of novel as well as existing Dutch compounds in comprehension. We visually presented compounds containing interfixes that were either in line with the bias of the left constituent family or not. In the case of existing compounds, we also presented variants with replaced interfixes. As in production, the bias of the left constituent family emerged as a crucial predictor for both acceptance rates and response latencies. This result supports the hypothesis that, as in production, constituent families are (co-)activated in comprehension. We argue that this co-activation is part of a supralexical inferential process, and we discuss how our data might be interpreted within sublexical and supralexical theories of morphological processing.