The vacuolar H⁺ pumps (H⁺-ATPase and H⁺-PPiase) play a fundamental role in the physiology of plant cells. By pumping H⁺ into the vacuole and driving the secondary active transport of cytosolic various ions and metabolites into the vacuole, they contribute to the prevention of cytosolic acidification and maintenance of cell water and nutrients. Studies that have been performed during the last fifteen years have revealed that a variety of plant species increase the potential activity(ies) of vacuolar H⁺ pump(s) (H⁺-ATPase and/or H⁺-PPiase) under stressful conditions (i.e., high salinity, toxic metal stress, anoxia, chilling stress, and nutrient deficiency), and this has resulted in a discussion that increases in potential activity(ies) of vacuolar H⁺ pump(s) under such stresses may be advantageous for plant survival in nature. The reported responses of vacuolar H⁺ pump activity to stresses, the physiological meanings and some mechanisms responsible for the responses are described here together with my personal views of them.