Over the last two decades, the Drosophila larval neuromuscular junction (NMJ) has gained immense popularity as a model system for the study of synaptic development, function, and plasticity. With this model, it is easy to visualize synapses and manipulate the system genetically with a high degree of temporal and spatial control, which makes it ideal for resolving problems in synaptic physiology and development. This article describes a procedure for labeling various proteins with antibodies in dissected larval body-wall muscles and visualizing their localization and distribution in the brain, NMJ, and muscle.