The gas tank retaining device of the present invention is particularly usable for retaining oxygen cylinders with respect to emergency equipment such as mobile stretchers that need to be transported in vehicles. Security of heavy oxygen or gas tanks is achieved by providing a housing with an access opening and a uniquely configured locking mechanism for retaining a generally cylindrical tank preferably in a horizontal orientation. The locking mechanism is steady state biased in a closed or retaining position for holding the tank within the housing and can be moved to a releasing position responsive to manual manipulation thereof.
