Active avoidance of harmful situations seems highly adaptive, but the underlying neural mechanisms are unknown. Rats can effectively use the superior colliculus during active avoidance to detect a salient whisker conditioned stimulus (WCS) that signals an aversive event. Here, we recorded unit and field potential activity in the intermediate layers of the superior colliculus of rats during active avoidance behavior. During the period preceding the onset of the WCS, avoids are associated with a higher firing rate than escapes (unsuccessful avoids), indicating that a prepared superior colliculus is more likely to detect the WCS and lead to an avoid. Moreover, during the WCS, a robust ramping up of the overall firing rate is observed for trials leading to avoids. The firing rate ramping is not caused by shuttling and may serve to drive downstream circuits to avoid. Therefore, a robust neural correlate of active avoidance behavior is found in the superior colliculus, emphasizing its role in the detection of salient sensory signals that require immediate action.