Warning signs and labels are on many consumer products and in many public places, and in this increasingly technical world, these warning messages often provide critical information necessary to one's safety. But, many Americans cannot read English. Graphic symbols have been suggested as a means of communication with these users as well as those who can read. Three experiments regarding the effectiveness of pictograms in warnings were conducted. Experiment 1 investigated pictogram identifiability. Identification rates ranged from 2 to 95%. Experiment 2 studied pictogram communication of injury avoidance information. Pictograms did not uniformly cue this information. Experiment 3 investigated how pictograms affect hazard perception. The presence of a pictogram in a warning message was found to increase perceptions of hazard, especially where an external, easily-represented hazard referent was concerned. It is concluded that pictogram comprehension is a function of identifiability as well as injury communication and hazard perception.