A dominant feature of optimally and underdoped cuprates is the appearance of a pseudo gap in the normal state excitation spectrum. The microscopic mechanism which is responsible remains a mystery. A number of scenarios for explaining the pseudo-gap have been pro- posed (see Ref. (1) for a recent review). However no cal- culations of the consequences of a large applied field for the pseudo-gap have been published. The high magnetic field behavior of the pseudo-gap provides additional ex- perimental characterization of the pseudo-gap which is crucial for differentiating between various pictures.