Abstract: Individual groups of inflatable cushions forming an air mattress are supplied with pressurizing air through a common feed duct having an upstream on/off valve and individual on/off valves in branch ducts leading to individual groups of cushions. When the upstream valve is open, it exhausts pressure air from the branch ducts so that if any one of the branch duct valves is also open, its associated group of cushions are subjected to reduced pressure. The individual valves may be operated to isolate groups of cushions from each other while the upstream valve is closed and thus subject a particular group of cushions to system pressure. A single pressure sensor measures the pressure to which the particular group of cushions is subjected and the whole system may be programmed though a computer for automatic control dependent upon individual user requirements.