An interlaboratory comparison study was undertaken to examine the spread in concentrations obtained when using diffusive samplers to monitor ambient air concentrations of selected volatile organic hydrocarbons at common sampling sites. Perkin-Elmer tube-type diffusive samplers were employed. Samplers from 12 participating laboratories were exposed during a 1 week period at two sites in Sweden, one urban (Gothenburg) and one rural (Rörvik). The tubes were then analysed by the respective laboratories using a common standard. Results from the statistical interpretation of the data are presented. Variations in mean concentrations among the laboratories were greater at the rural site than at the urban site, with RSDs from the mean of all mean values of about 50 and 40%, respectively (outliers omitted). Even the intralaboratory repeatability varied widely among the participants, from 2% to 73%(outliers removed). Possible causes for the variations are discussed.