Air pollution is responsible for a variety of respiratory ailments. Motor vehicles produce about 60 percent of smog-forming emissions in California. While pollution levels have decreased in the last 30 years, further steps must still be taken to reduce pollution from motor vehicles. California already has the world's cleanest standards for new light-duty motor vehicles and gasoline. Low-emission vehicle regulations will require conventional vehicles to become steadily cleaner until 2010. This will largely result from refinements to existing technologies. Further refinements to gasoline are under consideration. California will require the marketing of zero and near-zero emission vehicles in 2003. Battery-powered electric vehicles are already available. Fuel cell vehicles show great promise and will be the focus of a major demonstration project in California. Hybrid electric vehicles and advanced internal-combustion engines also show substantial promise. Heavy-duty vehicles will be subject to new emission standards in 2004, but California is looking for additional strategies to reduce emissions from those vehicles. The use of low-sulfur diesel fuel and incentives for fleet operators to use alternative fuels are desirable strategies.