Peripheral receptive fields are described for 130 neurons in the anterior (ASG) and posterior (PSG) sigmoid gyri of cats that, after being held under general anesthesia during operative manipulations, were locally anesthetized and immobilized with a neuromuscular blocking agent. Modalities tested with hair-bending, touch, pressure and joint movements. The spatial extent and effective modalities of such receptive fields during continued testing were either fixed or labile; neurons of the latter group became receptive to new influences. Labile fields returned to their initial states on cessation of stimulation. In the ASG slightly more than half of all pyramidal tract (PT) cells and non-PT cells had fixed fields, as did PT cells in the PSG, but receptive fields of postcruciate non-PT cells were all fixed. Both fixed and labile fields could be initially local or else wide. Fixed local fields referred only to contralateral parts of the body, while other fields often included ipsilateral projections. Neurons with fields of the former type were modality-specific, but others could be multi-modal. Receptive fields of adjacent cells overlapped or were situated closely together and were of the same type, excepting lability of postcruciate non-PT cells.