When a wet wool fiber is strained to a fixed extension, allowed to remain at this extension for a time, and then dried, the stress in the fiber rises. This rise of stress is independent of the time as long as it is greater than about 1 min. and is also independent of a number of chemical and physical modifications to various fibers. The rise in stress is dependent on the strain and increases to a maximum value at about 30% strain. Between 30% and 50% strain no further increase was recorded. From the evidence presented, it is suggested that drying the fiber in a strained state introduces strained hydrogen bonds, which are responsible for the stress rise on drying.