Attention to a visual target can affect perception of a subsequent target for half a second, increasing its sensitivity to backward masking (the attentional blink, AB). In 6 studies, we compared the AB when the second target and its mask had a common onset and when the mask appeared after the target. The results indicate that common-onset masks do not produce large ABs even when there is a feature change or an interruption of the mask after the target but do produce a large AB if the location of the mask is changed. The data suggest that new object onsets reduce conscious access to unattended targets.