Our research aims at exploring psycholinguistic processes implicated in the speech-in-speech situation. Our studies focused on the interferences observed during speech-in-speech comprehension. Our goal is to clarify if interferences exist only on an acoustical level or if there are clear psycholinguistic interferences. In 3 experiments, we used 4 talkers cocktail-party signals using different world languages: French, Breton, Irish and Italian. Participants had to identify French words inserted in a babble noise. Results first confirmed that it is more difficult to understand a French word in a French background than in a babble composed of unknown languages. This result demonstrates that the interference effect is not purely acoustic but rather linguistic. Results also showed differences in the observed performances depending on the unknown language spoken in the background and demonstrated that some languages interfered more with French than some others.