In this presentation some of the more recent results in frame-to-frame coding of television will be reviewed with an eye toward pointing out the advantages and disadvantages of applying these techniques to image transmission or image storage. Interframe coding, as the name implies, takes advantage of frame-to-frame redundancy in a television signal, of which there is a considerable amount, if movement is not excessive in the scene being televised. In videotelephone or conference TV applications, for example, it has been known for some time1,2 that 1 MHz, 271-line, monochrome signals can be coded using between 3/4 and 1 bit per picture element (pel) or 1.5 to 2 megabits per second compared with 16 Mb/,s required for 8-bit PCM. This bit-rate reduction is possible because in videotelephone or TV conferencing, the cameras are usually stationary with very little zooming or panning taking place, with the result that the pictures produced typically contain large stationary areas which do not change from frame to frame. These areas do not have to be transmitted. At the receiver they can be obtained simply by repeating the information from the previous frame. Transmitting only the pels which change significantly from frame to frame is called "conditional replenishment."