Only a small amount of information on cigarette deliveries of formaldehyde and hydrogen cyanide, and on their filtration behaviour, is available in the literature. Previous methods have used cold traps or liquid traps the large volume of which may seriously affect puff profiles. A simple solid trap is described from which both compounds can be easily extracted for subsequent colourimetric determination using an autoanalyser. Some typical cigarette deliveries are quoted which show the effect of tobacco type, filter type and levels of ventilation on formaldehyde and hydrogen cyanide deliveries.