The nematode Caenorhabditis elegans has long been popular with researchers interested in fundamental issues of neural development, sensory processing and behavior. Recently, advances in applying electrophysiological techniques to C. elegans have made this genetically tractable organism considerably more attractive to neurobiologists studying the molecular mechanisms of synaptic organization and function. The development of techniques that involve voltage-clamp of specific neurons and muscles has allowed the coupling of genetic perturbation techniques with electrophysiological analyses of nervous system function. Recent studies combining these biophysical and genetic techniques have provided novel insights into the mechanisms of presynaptic neurotransmitter release, postsynaptic responses to neurotransmitters and information processing by neural circuits.