The purpose of this study was to investigate the deterioration of tin ingots recovered from a late 14th century B.C. (Late Bronze Age) shipwreck off Ulu Burun (Kas) Turkey. As so little elemental tin has been excavated from underwater sites and preserved to date, the Ulu Burun ingots offer a unique opportunity to study the degradation products of ancient tin artifacts from a natural marine environment. The current investigation had three major objectives: to identify corrosion products; to confirm or refute the presence of tin pest, which has been asserted as one of the major reasons for the disintegration of the ingots and a topic of much controversy in the conservation and museum communities; and, finally, to contribute to the overall understanding of marine tin. The following instrumental techniques were used to analyze ingot samples: x-ray diffraction, atomic absorption, inductively coupled plasma emission spectroscopy. The results of the analysis have identified corrosion products that are characteristic of the type of products anticipated on tin objects from a marine environment. The presence of the controversial tine pest disease was confirmed in two of the six samples tested. Sample preparation appears to be a potential factor in the determination of tin pest using XRD.