Abstract: A high pressure bellows assembly installed in a valve which includes a housing, inlet and outlet ports connected by a passageway, a valve seat in the passageway, a valve stem movably supported on the housing and extending into a pressure chamber in the housing and having a valve plug engageable with the valve seat; the bellows assembly including a pair of bellows segments arranged in tandem along the valve stem in the chamber and sealingly interconnected by a floating collar. One end of the bellows assembly is sealed to the housing, and the other end sealed to the valve stem. Restraining members are disposed exteriorly of each bellows segment to limit expansion of the bellows segments and support them laterally. The restraining members at one end of the bellows assembly are fixed relative to the housing while the restraining members at the other assembly end are fixed relative to the stem.