Okadaic acid (OA) and its analogs, the dinophysistoxins, are potent inhibi-tors of protein phosphatases 1 and 2A. This action is well known to cause diarrhea and gastrointestinal symptons when the toxins reach the digestive tract by ingestion of mollusks. A less well-known effect of these group of toxins is their effect in the cytoskeleton.