Sulfur levels in both gasoline and disel fuels are being restricted because of environmental pollution concerns throughout the world. The U.S. Environmental Protection Agency has mandated the levels of sulfur which may be allowed in most road and off-road vehicles. Although there are many standard test methods available for determining sulfur in petroleum products, presently only about four can qualify for their usefulness at the expected low levels in the future fuels. A large interlaboratory study undertaken by ASTM to estimate the capabilities of these methods is described. Also, data from the ASTM interlaboratory crosscheck programs is reviewed to identify the trends that the industry laboratories are showing. Finally, a brief overview of some new methods being developed in the industry for such analyses is presented.