Presents analyses of resinous substances from 15th- and 17th-century shipwreck sites excavated in waters off Thailand and Saipan. Fourier transform infrared spectrometry, gas chromatography, and mass spectrometry were applied to the problem of identifying resins from three wrecks in the Gulf of Thailand and a Manila galleon off Saipan Island in the Marianas Island chain. The three samples from one of the Southeast Asian ships and the Manila galleon shipwreck site have been identified as derived from a <i>Styrax</i> sp. tree, probably <i>Styrax benzoin</i>. Samples from two of the southeast Asian ships are triterpenoid resins, possibly from dipterocarp trees, which were found as sealants used to attach lids on large storage jars and as caulking between ship timbers. Based on historical accounts and the ethnographic record, resin benzoin has been considered an important incense and medicinal resin since ancient times. It was traded north to China from at least the 13th century and was exported from Bangkok and Hanoi earlier in this century. On both the Saipan wreck (with two large storage jars which contained <i>S. benzoin</i>) and one of the Southeast Asian ships the resins were most likely trade goods. This analysis establishes that resin benzoin can survive in aqueous archaeological contexts for considerable spans of time without significant deterioration.