An adaptive speech and channel coding scheme is described, applicable to the communication of intelligible speech over very narrowband, noisy channels. A fixed- channel bit rate of 1200 bits per second (b/s) is assumed and the channel Eb/N o can drop below 3 decibels. A family of speech coders, derived from a parent coder operating at 1200 b/s, is described which, when combined with a variable rate (punctured) convolutional code, yields an adaptive system capable of operating over a range of channel conditions. The locations of the channel Eb /No threshold points between the various schemes were derived through simulation.