An experimental test facility was constructed to test and verify the operation of two parallel arrays of anisotropically micromachined (etched) micro heat pipes (MHPs) on a single crystalline (100) semiconductor silicon wafer. A micro heat pipe is a small-scale device used to transport energy from a heat source to a heat sink in nearly isothermal operation. The individual MHP was an isosceles triangle with a length of 25.4 mm, and a width of 100 am and 260 mu m far the arrays. A 7740 pyrex glass wafer was used to seal the pipe array hermetically. The transparent glass allowed visual inspection of the level of the working fluid filling the pipe array. Two working fluids were tested, pure water and methanol. A Kapton healer was used to supply the heat input, and cooling water flowing through the condenser (to remove the applied heat) was used as a heat sink. Filling charges of 5%, 10%, 20%, 30%, 50%, and 80% were tested The axial temperature drop along the length of the pipe was measured using K-type thermocouples connected to a data acquisition system. Fourier's law was used to calculate the effective thermal conductivity. The results showed a maximum improvement of 11% in effective thermal conductivity at higher power levels. However, the theoretical model predicted an improvement of at least 193%. An optimum fill of 5% was identified. The results are compared to earlier published data of Duncan from Peterson's group at Texas A&M.