S. Yantis and A. P. Hillstrom (1994) have claimed that abrupt onset of a new visual object captures attention even when the new object is equiluminant with its background, implying that attention is captured at the level of object descriptions rather than at the level of luminance change detection. S. Yantis and A. P. Hillstrom's experiments contained potential flaws that call their conclusion into question. The present article reports 5 experiments investigating these and related issues. The results suggest that for abruptly onsetting visual objects to capture attention, detection of change in a dimension of sensory stimulation is a necessary, but perhaps not a sufficient, requirement. Evidence is also presented against the view that attentional priority for new objects arises as a result of visual masking of old objects in the same displays.