The microparticulate (i.e., aerosol) and gas concentrations in Arctic air masses are being assessed currently as a result of a large-scale, multinational cooperative study made this spring. It turns out that many of the ideas about the origin of Arctic haze, industrial pollution, soil particles from the great desert regions of eastern China and Mongolia, and seasonal effects, to name a few, may all be valid. A recent report about the first extended airborne measurements of Arctic haze that were made during March and April of this year stated: “Most of the scientists on board the NOAA plane found the haze to be much denser and more extensive than they anticipated” (Environ. Sci. Technol., June 1983). The results of WP-30 Orion research aircraft flights over the Arctic ice cap suggest that in some locations the haze extends upward of 8.5 km at this time of the year. The haze was found to exist at all latitudes in the northern polar region with unbroken continuity to an altitude of approximately 3 km. At higher altitudes there was a banding of discontinuous haze layers.