There is disclosed the combination of an inflatable inner sole and a supporting underlayment for footwear, such as a shoe, boot or sandal. The inflatable inner sole is formed of upper and lower plastic sheets having the shape and size of a sole and bonded together in a continous seam about their peripheral edges thereby forming a sealed interior. A plurality of this continuous seams are formed between the upper and lower sheets to create within the sealed interior a plurality of interconnecting tubular passageways. The inflatable inner sole is provided with an air pump that preferably is mounted at the heel of the inner sole. The air pump is a flexible bulb with an inlet valve and discharges into a flexible tube which extends to a pressure control valve and then to the interior chamber of the inflatable inner sole. The pressure relief valve is manually adjustable to control the pressure within the inflatable inner sole. Excess air from the pressure control valve is directed into channels formed on the undersurface of the inner sole where it discharges through sealed apertures in the inner sole thereby providing forced air circulation in the shoe. Alternatively a manually operated air pump can be provided and the inner sole can be provided with inflatable upper linings for the shoe or boot.