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Although 4-month-olds perceive continuity of an object's trajectory through occlusion, little is known about the information specifying an occluding surface at this age. We investigated this in 3 experiments involving 84 participants. Testing the claim that 5-month-olds are unable to perceive the Kanizsa figure as an occluding surface (Csibra, 2001), we demonstrated that 4-month-olds perceived trajectory continuity behind this figure providing its horizontal extent was small. We demonstrated that the presence of visible occluding edges or occlusion of background was insufficient to specify an occluding surface but that their combination was sufficient. Thus, beyond object deletion and accretion, both visible occluding edges and occlusion of background are necessary for perception of occluding surfaces at this age.