A multiple regression single element tracer method was used to estimate source contributions to fine and coarse aerosol mass and light extinction, measured in Denver during January 1982. Motor vehicles were the largest contributor to average fine particle mass (42%) and daytime light extinction (47%). Electric power generation was next largest, at 23% and 44%, respectively. Estimates were generally similar to those of the comprehensive field study conducted by General Motors Research Laboratory in late 1978, but with a somewhat enhanced motor vehicle contribution compared with the 1978 results. Notable differences from the 1978 results included a reduced value for b(sup ap)/b(sub sp) (0.24), a reduced value for the ratio of elemental carbon to fine particle carbon (0.23), and an absence of non-sulfate sulfur in the fine mass fraction. The differences are in the direction of lessening the distinctiveness of Denver relative to other U.S. airsheds.