The problem of the study is to determine whether the aural mechanism, shown in 1944 to be the basis of ''obstacle sense'', is auditory or cutaneous, or whether both are involved. Subjects with no outer ear defects who were deaf-blind were chosen. The task was to determine whether the cutaneous surfaces of the meatuses and tympanum were sufficient to the perception of obstacles. Subjects who posssssed the ability to get about alone to a high degree were chosen for the 1st expt., in which a high stone wall with a high coefficient of reflection was used as the obstacle. One of 10 subjects gave indications of possessing an obstacle sense. When secondary cues from the floor, etc., were removed the same subject still possessed the ability, which was eventually traced to visual cues (some light-sense remained in one eye). Under conditions in which all possible cues except ''pressure'' were eliminated, all subjects made uniformly bad scores. Deaf-blind subjects do not possess an ''obstacle sense'' and are, incapable of learning it. The pressure theory is untenable; auditory stimulation is both necessary and sufficient for the perception of obstacles by the blind.