The use of toxic chemicals within museums is an issue only recently addressed by anthropologists and scholars in related fields. A case of arsenic poisoning in an anthropologist during the 1960s is reviewed for what it may tell us about a mysterious ailment that afflicted Clark Wissler 50 years earlier. While no conclusive diagnosis can be made, Wissler’s case reminds us that we have come a long way in protecting against one of the lesser known dangers confronting anthropologists. All museums use pesticides and preservatives of some form, though the health impact of these agents is not always known. This necessary evil in the preservation of ethnographic collections can thus pose a health risk to people who work with or come in contact with treated objects. Here we open one cold case file, in which we believe a prominent American anthropologist may have directly suffered from the effects of poisons commonly used in the early nineteenth-century. Our own experience and recent inquiries provide one possible answer to the cause of the illness suffered by Clark Wissler