This paper reviews the results from the plasma wave instrument on the Dynamics Explorer 1 (DE 1) spacecraft. The DE 1 spacecraft was launched on August 3, 1981, into an elliptical polar orbit with initial perigee and apogee radial distances of 1.09 and 4.65 RE. In the roughly 6 years since the launch of the spacecraft, DE 1 has provided basic new information on a wide variety of magnetospheric plasma wave phenomena. These include auroral kilometric radiation, auroral hiss, Z mode radiation, narrow-band electromagnetic emissions associated with equatorial upper hybrid waves, whistler mode emissions, wave-particle interactions stimulated by ground VLF transmitters, equatorial ion cyclotron emissions, ion Bernstein mode emissions, and electric field turbulence along the auroral field lines. We first give a brief review of the basic plasma wave modes that can exist in the equatorial and polar regions of the magnetosphere. After the basic terminology is established, each of the above areas of plasma wave research is discussed in detail, first by reviewing the state of knowledge at the time of the DE 1 launch and then by describing the contribution made by DE 1 in the 6 years since the spacecraft was launched.