We have developed an original method of determining the rectal and the anal compliance. The rectum must serve as a fecal reservoir. This storage function requires that the rectum must be distensible. The anal canal must become easily looser for defecation. These features are not explored by the usual rectoanal manometric recordings. Very few investigations about the compliance are carried out. In our procedure, exploration balloons are connected via polyethylene tubes to pressure transducers, direct-writing electrical recorder and pump under the command of the computer. The pressure generated is as high as the distensibility is poor, as the compliance is decreased. The pressure/volume curve shows the compliance. The procedure is different for the rectum on the one hand, and for the anal canal on the other. The rectal device consists of a balloon at the end of the tube. It shall be inflated until only 60 ml., and then deflated at the same rythm, which is constant during each test. The first test takes place at the speed of 30 ml. per minute; so the inflation lasts 2 mn and the deflation the same time, afterwards the second test lasts one mn for each one, and finally the third one 40 seconds in the same way. For the anal canal, the balloon, ring shaped around the tube, measuring an inch in length, is inflated at only 12 ml. For the first test the inflation and deflation rate of speed is 3 ml per mn, afterwards 6 ml./mn then 9 ml./mn. and thereafter 12 ml./mn/; these series are done in randomized order. In both procedures, an additional relaxation test at the maximum of inflation takes place for 2 minutes. We have explored ten healthy volunteers and 120 patients suffering from various digestive diseases. The curves show the rectal compliance, and in the case of the anus a relaxation, which seems to be an active opening, occurs for a distension of 5-8 ml, i.e. 19-21 mn in diameter. In pathology, the excess of compliance is observed in patients with incontinence, whereas an inadequate compliance is seen in the dyschesia, descending perineum and prolapse, traumatic or surgical injuries, etc. This exploration will be a useful guide for the choice of the convenient treatment and the follow-up.