Eight individuals with calcified cysts preserved in the thorax and abdomen, one of which had a maximum diameter of 17–20 cm, were recovered during recent excavations at Skriðuklaustur, a medieval monastic site which also functioned as a hospital during its operation from AD 1493–1554 in Eastern Iceland. Hydatid cysts are the result of parasitic infection by Echinococci commonly in the liver and lungs of the accidental human host. Echinococcus granulosus was likely introduced to Iceland soon after the settlement period (9th century AD) and became endemic around AD1200 when dogs were introduced from Germany. It has since been eradicated in Iceland due to an extensive educational literature programme and government controls implemented since the mid-1800s. Reviews of the palaeopathological literature mentioning calcified shell fragments indicated hydatism to be the most logical aetiology. The eight individuals in question were buried in close proximity to one another. This may indicate that this particular ailment (sullaveiki) had its own classification during the medieval period in Iceland and perhaps even a distinct treatment if not in life, at least in death. Copyright © 2010 John Wiley & Sons, Ltd.