Trophallaxis, defined as the direct transfer of alimentary liquids, including suspended particulates and derivatives, from one nestmate to another via regurgitation or anal feeding, is important in the nutritional dynamics and communication of many social insects. Trophallaxis is a mechanism for the transfer of nutrients, symbionts, pheromones, and information within social insect colonies. We ... [Show full abstract] used the radioactive tracer cobalt-60, combined with the vital dye Nile Blue A, in a standard diet to investigate the rate, amount, and distribution pattern of alimentary liquids in the termites Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae), R. virginicus (Banks), and Zootermopsis nevadensis subsp. nevadensis (Haverty & Thorne) (Termopsidae). The technique did not affect termite survivorship and enabled determination of the rate and quantity of material transferred from identifiable, marked “donor” individuals to “recipients.” This method of tracing trophallactic transfer of alimentary fluid would be an appropriate standardized technique facilitating comparison of data among researchers. Transfer of a detectable amount of alimentary fluid in R. flavipes, R. virginicus, and Z. n. subsp. nevadensis occurred within 6–12 h after introduction of potential donors to potential recipient termites. The amount of isotope transferred from the donor to the recipient group varied, but generally ranged from 5 to 30% of the isotope initially acquired by the donor. Transfer of isotope initially was to a few members of the recipient group; isotope acquired by those recipients was distributed subsequently among the other termites. Differences in patterns of trophallaxis between Isoptera and Hymenoptera are discussed.