By the use of a gold-plated silver sample holder, and aRuO2-Cernox combination thermometer, low-temperature specific-heat measurements in the temperature range from 0.35 to 90 K, and in magnetic fields up to 17.5 T, have become possible with remarkably improved accuracy. At 500 mK, the lower limit for the heat capacity that can be measured amounts to 0.02 mJ/K. The sensitivity in that case is about 0.3 &mgr;J/K. The error margin is 1&percent; for large heat capacities (larger than twice the sample-holder contribution) at higher temperatures, increasing to 3&percent; for small heat capacities (half of the sample-holder contribution) around 500 mK. In high fields, for accurate measurements (error <3&percent;) the temperature range is restricted to above 0.5 K. ©1997 American Institute of Physics.