Nuclear heat deposition rates in ten different materials, Li2CO3, Graphite, Ti, Ni, Zr, Nb, Mo, Sn, Pb and W, subjected in D-T neutrons have been measured by a microcalorimetric technique in the frame work of JAERI/USDOE collaborative program on fusion neutronics. A great improvement in accuracy of experimental data was achieved by introducing a high sensitivity voltmeter and applying constant current on the thermal sensors. The measured heating rates were compared with calculations to verify the adequacy of the currently available data base relevant to the nuclear heating process. In general, calculations with data of JENDL-3 and ENDL-85 libraries gave excellent agreements with experiments for all materials except Zr. The calculation with the MBCCS suffered large discrepancy from measurement.