The performance characteristics of the lead dioxide (Huey) plate for sampling sulfur dioxide are evaluated, and a method for determining sulfur dioxide as precipitated barium sulfate by weighing on an electrobalance is described. The data produced by exposing Huey plates over a two-year period are presented. A direct relationship between the concentration of sulfur dioxide in the ambient atmosphere as determined by continuous automatic monitoring and the mass loading of lead sulfate on the Huey plate has been confirmed. The correlation coefficient for the relationship was 0.90.