A new method for sensitive, specific, and direct determination of palytoxin is proposed herein. It is based on combination of reversed-phase liquid chromatography with mass spectrometry (LC-MS). The new method was set up on a turbo ion spray-triple quadrupole MS instrument operating in selected ion monitoring (SIM) and multiple reaction monitoring (MRM) acquisition modes (positive ions). The minimum detection levels for matrix-free toxin on column were thus estimated from the data to be 200 and 125 pg in SIM and MRM modes, respectively. Spiking experiments before and after extraction allowed us to assess limits of detection and quantitation for palytoxin in matrix, accuracy, and intraday and interday reproducibility of the method. The developed method was decisive for the analysis of a plankton sample collected along Genoa coasts in July 2005 when respiratory illness in people exposed to marine aerosols occurred. It is suggested that putative palytoxin was the causative agent responsible for patients' symptoms and demonstrated for the first time the presence of such a toxin in Italian waters.