A new class of drilling fluid has been developed and proved to be extremely effective in increasing the leakoff pressure in permeable formations. A simple laboratory test is described to assess the limits of potential increase of leakoff pressure in the field. This paper describes some fundamental issues regarding fracture and leakoff pressures for well construction purposes and then shows how the increase in leakoff pressure can be achieved with the use of this new drilling fluid. Some case histories are presented in which the fluid has proven to increase the leakoff pressure effectively, and a comparison is made with drilling fluids traditionally used, highlighting the limitations of the current fluids to effectively deliver what the industry really needs. Several applications are presented in which an increase in leakoff pressure can hugely reduce the costs and risks of the wells.