Porous glasses were prepared by phase separation and leaching of NaF, NaCl and NaBr containing sodium borosilicate glasses with low silica content. Each sodium halide was added to 10Na2O?50B2O3?40SiO2 (wt%) glass and the effects of the additive on phase separation and leaching were investigated. The mean pore diameter, specific surface area and porosity were 300-2500Å, 20-60m2/g and 55-56%, respectively. The pore diameter increased and the specific surface area decreased with increasing temperature, time of heat treatment and halogen content. It was found that the halogen containing specimens were leached out in shorter soaking time than the halogen free specimen and that chlorine addition was most effective. The change in the leaching rate is probably caused by the dissolution of halogen containing sodium borate phase into hot water. For chlorine containing sample, leaching finished in a half time that of the halogen free sample.