Shingles of western red cedar (<i>Thuja plicata</i>), western hemlock, sugar pine (<i>Pinus lambertiana</i>), and western larch (* 2Larix occidentalis* 1), untreated, or dipped in or brushed with PCP or CCA, were exposed outdoors at Corvallis, Oregon. The area is classified as intermediately favorable to decay of wood above ground. Additional dipped samples were exposed to intermittent water sprays equivalent to 0, 2, 7, and 17 years rain at Corvallis. After 3 years, shingles retained 0.21-0.80 lb/ft³ of CCA near weathered surfaces. Losses were greatest in sugar pine. Low retentions of PCP still retarded fungal growth. After five years, most treated shingles remained sound; a few cedar shingles were predisposed to rapid breakdown by collapsed springwood. Untreated western hemlock and pine shingles had begun to decay. -- AATA