A field test was conducted to study the feasibility of monitoring trace lead in shipments of unleaded gasoline by means of an X-ray fluorescence continuous low lead analyzer. Batches of unleaded gasoline were blended at the refinery and transported to distant terminals by tankers and by pipeline. The low lead analyzer was used to continuously monitor the lead content of the unleaded gasoline as it left the refinery and was received at the terminals. Field data of good precision were in agreement with the accepted ASTM D-3237 atomic absorption method. The standard deviation of the X-ray method is ±0.0029 g Pb/gal and the test repeatability is ±0.008 g Pb/gal. X-ray fluorescence appears to be the best practical method available to determine the average level of lead contamination in large volumes of unleaded gasoline in the field with accuracy and precision.