The relative importance of visual and auditory information in judging student comprehension during a reading lesson was tested by having 42 adult subjects observe videotape recordings of reading lessons with individual children and estimate student comprehension with visual information only, auditory information only, or both visual and auditory information. The dependent variable was the accuracy of the estimates as measured by their agreement with the students' self-reported comprehension. Results showed that the greatest accuracy of decoding occurred in and visual-only condition, with the auditory-visual condition yielding significantly less accuracy, and with the lowest accuracy in the auditory-only condition. (Author/RL)