The influence of verbal and nonverbal contextual factors on intelligibility was examined using sentences produced under varying conditions by a speaker with severe flaccid dysarthria. Contextual factors included (a) concurrent production of communication gestures, (b) predictiveness of message content, (c) relatedness of sentences to specific situational contexts, and (d) prior familiarization with the speaker. Sentences produced by the speaker were audio- and video-recorded and presented to 96 listeners/viewers who were assigned to three different methods of presentation of the stimuli: (a) audio+video, (b) audio-only, or (c) video-only conditions. Results indicated that gestures, predictiveness, and context influenced intelligibility; however, complex interactions were observed among these factors and methods of presentation of the stimuli. Results were interpreted in light of Lindblom's "mutuality model," indicating that when signal fidelity is poor, as in the present speaker with dysarthria, differing combinations of signal-independent information may be employed to enhance listener understanding of spoken messages.