We propose a tactile-audio diagram, represented by a tactile pattern and linguistic information, as a new media for the blind. We have developed a vision substitution system which enables blind persons to read and write a diagram in the form of a tactile-audio diagram. The system consists of a personal computer, a tactile display with digitizer, an auditory information input/output device, and a command keyboard. The features of the system are: 1) the use of multimodality, i.e., tactile and auditory senses are used for perceiving spatial and linguistic information and 2) two-way communication, i.e., the system enables a blind person to read and write a diagram. This paper presents a tactile-audio diagram and an implemented prototype system based on this theory, along with a discussion and methods for enhanced representations.