We report on two brain-damaged subjects who exhibit the uncommon pattern of loss of object color knowledge, but spared color perception and naming. The subject P C O, as in previously reported patients, is also impaired in processing other perceptual and functional properties of objects I O C, in contrast, is the first subject on record to have impaired object color knowledge, but spared. Knowledge of object form, size and function. This pattern of performance is consistent with the view that semantic information about color and other perceptual properties of objects is grounded in modality-specific systems. Lesion analysis suggests that such grounding requires the integrity of the mesial temporal regions of the left hemisphere.