NMFS plans to issue proposed regulations to govern the unintentional taking of marine mammals, by harassment, incidental to military readiness activities conducted by the Navy in the Northwest Training and Testing Study Area. The proposed regulations will set forth the permissible methods of taking, other means of effecting the least practicable adverse impact on the affected species or stocks and their habitats (i.e., mitigation), and the requirements pertaining to the monitoring and reporting of such taking. Letters of Authorization issued under the 5-year regulations would authorize the take of marine mammals incidental to upcoming Navy training and testing activities to be conducted within the Study Area. Implementation of the above training and testing activities may expose marine mammals present within the Study Area to sound from active sonar and underwater detonations. NMFS' proposed rule, if issued, would cover take of individuals of 29 marine mammal species by Level B (behavioral) Harassment. Further, the proposed rule would cover some Level A (injury) harassment and mortality of marine mammal species over the 5-year period.