Novel Schottky in-plane gate (IPG) quantum wire transistors were fabricated for the first time, and their transport properties were investigated. For fabrication of transistors, an AlGaAs/GaAs quantum well wire (QWW) was produced by etching, and platinum LPG electrodes were directly formed on both edges of the QWW by a new in situ electrochemical process. The current-voltage (I-V) characteristics of the fabricated long-channel and short-channel devices exhibited good field effect transistor operation at 3-300 K. Simple theoretical models assuming either a constant mobility or a constant velocity were developed. They provide a reasonably good phenomenological description of the observed I-V characteristics. Limitations of the models are also discussed. At low temperatures, the short-channel device exhibited sharp quantized conductance steps in the units of 2e(2)/h near pinch-off, indicating one-dimensional ballistic quantum transport. The first plateau of the conductance step remained visible up to 40 K, which is the highest reported so far for the AlGaAs/GaAs system.