Studies of the biology, ecology, and potential of a nematode Filipjevimermis leipsandra Poinar and Welch as a biological control agent for the banded cucumber beetle Diabrotica balteata LeConte were initiated in 1978 at Charleston, SC. Parasitism of the beetle larvae by the nematode was obtained in the field as early as the 1st week in Mar. and as late as the 1st week in December. Most parasitism occurred during periods of high rainfall and high temperature; parasitism was highest in Sept. and early Oct. As many as 23 postparasitic nematodes were obtained from a single larva. Body lengths of post parasitic nematodes ranged from 15 to 62 mm; the number of eggs deposited correlated with the length. As many as 7000 eggs were obtained from one nematode. Parasitism of the insect was obtained in the laboratory by exposing 1st instars to field collected soil or to potting soil with F. leipsandra eggs. The amount of parasitism obtained from a given number of beetle larvae and nematode eggs varied considerably despite our attempt to control the conditions as precisely as possible. The most post parasitic nematodes were obtained from soil that received the highest levels of nematode eggs.