Two factors said to produce varying levels of dramatic suspense are examined: degree of perceived outcome-uncertainty and audience disposition toward the hero-protagonist. In spite of the general consensus that these two factors affect suspense, there is wide disagreement as to the optimal level of viewer uncertainty regarding the hero's fate, and there is some question as to whether it is necessary for the viewer to be positively disposed toward the hero to produce a maximal level of suspense. To test competing claims, different versions of an audio-visually presented chase sequence were produced. Experimental materials were varied in a factorial design featuring the five levels of perceived outcome-uncertainty (hero's chances of success/survival = 0/100, 1/100, 25/100, 50/100, 100/100) and three levels of disposition toward the protagonist (neutral, mildly positive, strongly positive). Sex of viewer was included as a third factor. Degree of experienced suspense was assessed in viewer ratings. Both perceived outcome-uncertainty and viewer disposition variables yielded strong effects, though no significant sex differences were found. Rated suspense was at a maximum when the hero's chances of success/survival were perceived to be about one in 100 and minimal when either success or failure seemed absolutely certain. Further, suspense increased with increasingly positive dispositions toward the protagonist. Practical and theoretical implications of these results are considered.