Considerable concern has risen in the maritime community regarding impending regulations governing marine diesel emissions. The most immediate of these regulations is part of the MARPOL 73/78 Annex VI of the International Maritime Organization (IMO). The IMO has proposed a policy on the prevention of air pollution from ships to their 156 member nations. This treaty, much of which deals with large ships, states that NOx emissions should be restricted for smaller vessels as well. The policy, as drafted, would be effective for vessels whose keels are laid on or after Jan. 1, 2000. It is this deadline and the IMO approval process that has led to some confusion.