Simultaneous measurements of bext (teleradiometer), b(sup sp) (integrating nephelometer) and b(sup ag) (N02 monitor) were used to obtain particle absorption extinction coefficients b(sup sp) for the Denver atmosphere during January 1982. The average of the ratio bap/b(sup sp) was measured to be 0.185 + or - 0.015 at 530 nm, which is 2-3 times smaller than previous measurements. Supplementary data included b(sup ap) measurements by the integrating plate method, which yielded values systematically higher by about 35%, and elemental carbon (black soot) aerosol concentration, from which a value of 8.0 + or - 0.6 m sq/g-1 was obtained for the mass-specific absorption coefficient of elemental carbon.