Inattentional blindness describes the failure to detect an unexpected but clearly visible object when our attention is engaged otherwise. It needs to be investigated whether and how we process unexpected objects that go unnoticed. It was shown that although not consciously aware, characteristics of these stimuli can interfere with a primary task: Classification of to-be attended stimuli was slower when the content of the task-irrelevant, undetected stimulus contradicted that of the attended, to-be-judged stimuli. According to Lavie’s Perceptual Load Model irrelevant stimuli are likely to reach awareness under conditions of low perceptual load, while they remain undetected under high load as attentional resources are restricted to the content of focused attention. In the present study we investigated the applicability of Lavie’s predictions for the processing of stimuli that remain unconscious due to inattentional blindness. We try to replicate that unconsciously processed stimuli can interfere with intended responses. Furthermore, we expect the interference effect to be reduced under high perceptual load, as high load is thought to inhibit the processing of the unnoticed objects and therefore the occurrence of an interference effect.