A method is described for estimating oral toxicities (mug/g) of slow-acting toxicants against subterranean termites, Coptotermes formosanus Shiraki and Reticulitermes flavipes (Kollar). Groups of termites were fed with a known amount of medium containing a dye marker and a toxicant. Marked termites were evaluated for daily mortality after total consumption of the medium. Toxicant doses ingested by termites were derived from the total amount of toxicant in the feeding medium and the biomass of termites engaged in that feeding. Using oral LD50 estimates in mug/g, the total amount of toxicant required to control a field colony can be projected.