A gate valve includes a housing adapted to be installed in a pipeline, the housing having therethrough a flow passage, and a valve member mounted within the housing for movement between a first position, whereat the valve member closes the flow passage, and a second position, whereat the valve member opens the flow passage. The housing and valve member have axially spaced pairs of adjacent annular surfaces cooperating to define seals when the valve member is in the closed position. The housing has therein, adjacent one annular surface thereof defining at least one seal, a duct. Cooling air is introduced into this duct. The one annular surface of the housing has therein structure defining a gap for directing the cooling air from the duct against the respective annular surface of the valve member when closed or into the flow passage when the valve member is open.