The Drosophila larval neuromuscular junction (NMJ) shares many structural and functional similarities to synapses in other animals, including humans. These include the basic feature of synaptic transmission, as well as the molecular mechanisms regulating the synaptic vesicle cycle. Because of its large size, easy accessibility, and the well-characterized genetics, the fly NMJ remains an excellent model system for dissecting the cellular and molecular mechanisms of synaptic transmission. This protocol describes the steps for performing intracellular recording from fly larval body-wall muscles and explains how to record and analyze spontaneous and evoked synaptic potentials. Methods used include larval dissection ("filleting"), identification of muscle fibers and their innervating nerves, the use of a micromanipulator and microelectrode in penetrating the muscle membrane, and nerve stimulation to evoke synaptic potentials.