Experiments are performed to investigate the use of water-ethanol mixtures as a heat pipe coolant. An everted heat pipe structure consisting of a vertical tube, internally heated at the top, and around which is wrapped four layers of 325 mesh stainless steel screen, is used to measure the steady state and dryout heat fluxes as a function of mixture composition and capillary rise height. For small capillary rise heights it is observed that the maximum operating heat flux could be increased by 135% with waterethanol mixtures as compared to pure water. As the capillary rise height is increased the performance of water-ethanol mixtures becomes comparable to that of pure water. The measured dryout heat fluxes for pure water and pure ethanol are in reasonable agreement with the predictions of an analytical model which allows for two-phase flow, boiling, and dryout in the heated section of the wick.