The tar, nicotine, CO, HCN, total aldehyde, and acrolein deliveries of 102 brands of Canadian cigarettes have been determined. On the basis of these deliveries, 15 brands (9% of sales) were categorized as low hazard and 9 brands (10% of sales) as high hazards. All six constituents were used for the classification since for most brands tar was a poor indicator of gas-phase deliveries. As a result, smokers who indiscriminately switch to a brand with a lower tar delivery may inadvertently increase their exposure to gas-phase constituents such as CO and increase their risk of smoking-related pathology. With respect to Canadian cigarettes, the choice of a 30-mm standard butt length may result in omission of some of the available tobacco from the testing procedure, thus reducing the value of tar level as a guide to choosing a less harmful cigarette.