Most common phycotoxin poisoning syndromes have important neurological symptoms. However, little is known of the cellular and molecular targets of many of the phycotoxins that produce those human intoxications. We explore the effect of representative toxins on the membrane potential in human neuroblastoma cells by using a fluorimetric assay. Results presented in this study demonstrate that maitotoxin, palytoxins, brevetoxins, and ciguatoxins triggered a dose-dependent membrane depolarization. Mechanisms responsible for the toxins-induced changes in membrane potential are always related to a direct action of the compounds on membrane ion fluxes. This initial screening of the phycotoxins effect is the starting point to lately develop functional methods of detection.