Since television captioning first became available in Spain, advances have occurred on two fronts: a progressive increase in the number of programs with captions and improved captioning technology. The present study explores the effectiveness of captioning through analysis of deaf viewers' comprehension, taking into account the contribution of the program's verbal and visual information. The study participants, comprising two groups of deaf students at different educational stages, were asked to explain what they had understood after watching a film under two conditions: voice and sound but without captions; and voice, sound, and captions. Results indicate that deaf students have difficulty accessing the information even under the voice/sound/caption condition, not only due to their level of reading ability but also to the speed of caption presentation when oral content is literally transcribed on the screen in its entirety.