Generally, blind children, in particular the congenitally blind, find it difficulty to understand their surroundings. To help them, we have developed a computer assisted instruction (CAI) system which gives the blind spatial understanding. This system consists of a personal computer, an image-capture board, and a 3-CCD camera. We conducted an experiment using this CAI system on blind school students. A blind user was asked to arrange blocks of different shapes according to a problem presented by the system in the form of vocal instructions. When the user had completed the task of arrangement, the block layout was captured by the camera, and the shape and location of each block was analyzed, and the results output by speech. This CAI system, repeating problem presentation and task correction, may help blind children to gain spatial understanding without the help of sighted people.