To evaluate the suitability of a variety of fast voltage-sensitive dyes for optical recording of rapid transmembrane potential activity in the embryonic nervous system, we screened over twenty dyes, including several newly synthesized probes, in three different embryonic neural preparations: cervical vagus nerve bundle, nodose ganglion, and brainstem from 7-day old chick embryos. Measurements of voltage-related optical signals were made using a multiple-site optical recording system. Signal size, signal-to-noise ratio, photobleaching, and phototoxicity were examined. Several promising new merocyanine-rhodanine dyes for embryonic nervous systems were found.