A commercial formulation of Bacillus thuringiensis (Mattch) was evaluated under field conditions at Clemson, South Carolina, USA for control of the squash vine borer, Melittia cucurbitae (Lepidoptera: Sesiidae), on yellow crookneck squash, Cucurbita pepo in 1997, 1998 and 1999. Two application methods were used: injection of the B. thuringiensis formulation directly into the main stem and spray foliage application. These were compared to an insecticide standard, endosulfan (Phaser), and an untreated check. In most cases, B. thuringiensis treated plots had significantly less damage than untreated plots and generally gave control equal to that of the insecticide standard, enclosulfan. In a trial 1998, the two methods were directly compared, the foliage sprays gave control equal to or better than the injection treatments. Even during the heaviest pest pressure (second trial, 1998), the B. thuringiensis treatments were as effective as enclosulfan in reducing the squash vine borer damage.