Commercial timbers from Turkey used in coastal construction and boat building were tested for their resistance to marine wood-boring invertebrates in a marine trial and in a laboratory screening test. The timbers tested were beech (Fagus orientalis Lipsky), oak (Quercus petraea (Mattuschka) Liebl.), chestnut (Castanea sativa Mill.), and Scots pine (Pinus sylvestris L.). The marine trial was conducted over a period of 5 months at Mersin on the southern Mediterranean coast of Turkey. Activity by teredinid (Mollusca, Bivalvia) borers during this period was very high, resulting in the maximum rating of 4 on the EN 275 scale for P. sylvestris sapwood and heartwood panels. Q. petraea panels averaged 2.8 and C. sativa panels were attacked the least with a mean rating of 2.3. There was little variation between the timbers tested in the size of the shells of the teredinids found, and so variation in the level of attack can be ascribed to fewer animals colonising C. sativa and Q. petraea than P. sylvestris. About one half of the teredinids identified were Teredo navalis (Linnaeus 1758), one quarter Bankia carinata (JE Gray 1827), and one quarter Nototeredo norvagica (Spengler 1792). No evidence of preference for a particular timber by any of these species was observed. Teeth on the ridges of the shells of teredinids from C. sativa were partially or wholly immersed in a dark brown substance that might reduce the boring efficiency of the shell. Some attacking by limnoriids (Isopoda, Crustacea) was also detected. Specimens of the amphipod crustacean Chelura sp. were observed on panels of C. sativa. In a laboratory screening trial in which the feeding rate of individual Limnoria quadripunctata (Holthuis 1949) was assessed by measuring faecal pellet production, feeding on heartwood of C. sativa, F. orientalis, and Q. petraea averaged less than half of that on the non-durable sapwood and heartwood of P. sylvestris. The correlation between wood density and feeding rate was weak.