A study was conducted to determine the relationship between light absorption measurements from an aethalometer and a particle soot absorption photometer (PSAP) and black carbon mass concentrations across Canadian environments ranging from urban to remote areas. To achieve this, filter samples were collected for thermal analysis of black carbon simultaneously with light absorption measurements at several locations in Canada. Previously, it has been shown that the k relating particle light absorption to black carbon measured with an aethalometer changes with age, type, and composition of the aerosol, which varies with time and by space <Liousse et al., 1993; Petzold and Niessner, 1995; Lavanchy et al., 1999; Ruellan and Cachier, 2000>. Consequently, to convert light absorption measurements to the black carbon mass, the standard values used for k of 19 m2 g-1 for aethalometer and 10 m2 g-1 for PSAP, respectively, need to be fine-tuned to fit the conditions at the site of interest to obtain the site-specific attenuation, referred to as k(S.S.). Our results also indicate that k(S.S.) varies; on a broad scale, from remote continental to rural, suburban, and urban locations and from winter to summer and, on a small scale, within an urban area and from measurement to measurement at a single location. The range of median k(S.S) values observed was from 6.4 m2 g-1 to 20.1 m2 g-1. We suggest that the variability is connected to the distribution of sources and processes contributing to the carbonaceous aerosols at the sites.