In the next edition of the CSA O80 wood preservation standards, retention by assay rather than by gauge will be specified for chromated copper arsenate (CCA), ammoniacal copper arsenate and creosote. Based, in part, on the 14-year data from Forintek's field trials, these assay retentions will be lower than the old gauge retentions and lower than the assay retentions which had been specified in the AWPA standards (the AWPA independently introduced lower retentions for northerly waters in 1995). Continued testing is needed to confirm that the lower retentions will still provide the service life required from marine structures. The marine tests covered in this report were set up in 1978 in West Vancouver and in 1984 at two sites in New Brunswick. Red pine sapwood coupons (6 x 50 x 200 mm) were pressure treated with a range of retentions of preservatives which were listed in the standards at the time. They were suspended in the water column on metal racks and inspected once a year. Due to the poor state of repairs of the dock at Shediac the samples at this site could not be inspected at this time. At the West Vancouver test site coupons treated to the proposed assay retention with CCA (24 kg/m3) were in excellent condition after 17 years exposure. ACA treated coupons at the proposed assay retention of 30 kg/m3 had suffered from surface degradation by bacteria and fungi. While significant on a thin test coupon, such degradation on a marine pile or timber would have very little effect on the strength of the structure. Wrapping the ACA treated coupons for a period after treatment to simulate the drying rate of large dimension commodities did not improve its performance. Untreated coupons failed in less than a year at West Vancouver and between two and three years at Whitehead Island. At Whitehead Island, coupons treated to the proposed assay retentions with CCA and ACA were still performing well after 11 and 8 years exposure respectively (higher retention ACA added 3 years after experiment set up). Interestingly the pressure treated wood has performed better than the test racks. The racks at West Vancouver, made from 3.5mm thick carbon steel, had moderate corrosion after 10 years and had to be replaced after only 15 years.