The external, gregarious, braconid parasite, Allorhogas pyralophagus Marsh was mass released into field cages enclosing sugar cane infested with the pyralid, Eoreuma loftini (Dyar) to examine factors affecting parasitism rates and to assess the parasite's potential contribution to borer larval mortality. Three field experiments were conducted in July, September, and December, 1984. Total parasitism was 25.2% for the study and was the single most important source of borer mortality. Borers were equally susceptible to attack in leaf sheaths, whorls, and stalks in general, but larvae tunneling deep within stalks were parasitized less. An interaction between tunneling behavior of the borer and attack strategy of the parasite was important for parasite success. A. pyralophagus is probably unable to effect complete control of E. loftini in sugar cane because A. pyralophagus is physically unable to parasitize borers deep in the stalks. However, the parasite may be useful as part of an integrated pest management program, acting in concert with other parasite species, or attacking the borer in small-stemed grasses that serve as alternate host plants. none