In January 2010, the toxin-producing dinoflagellates Dinophysis acuminata and D. caudata (103 cells.l-1) were detected in Mar Azul during routine plankton monitoring in Buenos Aires Province coastal waters, Argentina. Wild clams Mesodesma mactroides and Donax hanleyanus from Mar Azul intertidal beach, which are part of the diet for local inhabitants and tourists, tested positive with the official lipophilic mouse bioassay. This paper focuses on the detection of Diarrhetic Shellfish Poison (DSP) toxins in these samples using a HPLC-FLD pre column derivatization procedure. The data showed that shellfish were contaminated with complex DSP toxin profiles composed of Okadaic Acid (OA), Dinophysistoxin-1 (DTX-1), Acyl-Dinophysistoxin-1 (Acyl-DTX-1) and Acyl-Okadaic Acid (Acyl-OA). The DSP toxins found in this study produce diarrhea symptoms consistent with those experienced by patients who had ingested cooked shellfish in January. This is the first report of Acyl-derivatives in South American Atlantic shellfish samples and of OA in Argentinean shellfish samples.