The aim of the present work was to determine the best conditions that elicit illusions of the McGurk type in French. We manipulated the item length (monosyllables vs bisyllables), the speaking rate of the bisyllables (slow vs normal vs fast), the vocalic environment (/a/ vs /i/), the voiced-voiceless characteristic of some stop consonants (/b/ vs /p/ and /g/ vs /k/) and the sound intensity (70 dB in the first experiment and 40dB in the second one). In both experiments, the effects were not affected by item length but, for the bisyllables, they increased at a slow speaking rate. The vowel /i/ gave rise to more illusions than /a/. Voiceless consonants produced more combinations than voiced ones, but in the case of fusions there was a tendency toward the reverse pattern. The percentage of illusion increased from the first to the second experiment: from 41% to 49% in the case of combinations and from 3% to 18% in the case of fusions. The McGurk effect was thus strongly affected by listening conditions.