A local absorbed dose calorimeter with certain novel features has been designed and constructed of A-150 tissue-equivalent (TE) plastic. The radiation absorption properties of this material and the relative absence of core impurities make the calorimeter suitable for use in a wide variety of radiation beams. The low thermal diffusivity of A-150 plastic led to the development of a unique spiral electrical calibration heater that has a mass of only 0.1% that of the core. The calorimeter can be calibrated in the quasiadiabatic or the heat-loss-compensated mode to test for possible effects caused by temperature gradients. The details of construction and operation are described.