The experimental measurement of nuclear heat deposition rates in a simulated D-T fusion neutron environment has assumed importance due to untested nature of large body of kerma factor libraries. An experimental effort was recently initiated to develop and apply calorimetric technique to measure heat deposition in various materials subjected to D-T neutron fields, in the framework of JAERI/USDOE collaborative program on fusion neutronics. Thermistors and platinum RTD's were employed as thermal sensors within calorimeters made of single materials (or probes). The first experiments were conducted during June 1989 and the tested materials included: Fe, Al, C, Cu. Each of these calorimeters was placed inside a vacuum chamber and the mean distance from the target was ∼8 cm. The calorimeters were subjected to spaced neutron pulses of 3 to 10 min duration. The measured heat deposition rates ranged from 7 to 30 µW/g for a normalized source strength of 1012 n/s-iron and graphite providing the lowest and the highest rates respectively. These single probe experiments were analyzed using 3D code MCNP. The single probe experiments were carried out again in december 1989. This allowed to verify the reproducibility. This time, the average target-probe distance was shortened to ∼5 cm which led to 2 to 3 times higher rates. Tungsten was also included. Ratio of computed (C) to measured (E) rates varied from 0.79 to 1.77 for RMCCS evaluation of MCNP. Four evaluations, available with MCNP, throw up large deviations; For example, C/E for iron for an experiment ranges from 0.40 to 0.94. In addition to single probe experiments, two novel experiments were conducted with multiple probes in separate host media of iron and graphite. C/E varied from 0.51 to 2.36.