Field tests were conducted in the summer of 1995 on four state-of-the-art temperature logging systems: an analog, electric-line, system; two pressure and temperature recording memory tools (in-hole computer systems); and a Distributed optical fibre Temperature Sensing (DTS) system. The tools produced accurate, detailed, temperature versus depth and temperature gradient versus depth logs at depths to 2 km and temperatures to 200 degrees C. Absolute temperature differences up to 0.4 degrees C were noted between tools. The computer and electric-line tools have significantly better precision and resolution than the DTS, but the DTS has the advantage of being able to measure temperature instantaneously throughout the hole, and would be well suited for monitoring dynamic systems and gas-filled wells. The multiple independent logs demonstrate that most of the "noise" seen in gradient logs is due to convection cells, which may have dimensions several times the borehole diameter, and that these convection cells are currently the limiting factor in resolving wellbore temperatures in most settings.