Two experiments examined the possibility that Mongolian gerbils with bilateral lesions of the striate cortex could use retinal image size as a distance cue on a jumping task. Systematically wider or narrower 'probe' landing platforms were inserted amongst regular training trials with a standard-sized landing platform. In both sham-operated and destriate animals, narrower platforms tended to produce overjumps of the leading edge of the landing platforms, while the wider probes tended to produce underjumps. The size of this effect did not differ between the two groups in either study. Differences between this type of task and traditional size discrimination experiments are discussed.