A series of test roofs clad with <i>P. radiata</i> shingles that had been pressure-treated with copper-chromium-arsenic and alkyl ammonium compounds was installed at a Forest Research Institute test site in Rotorua in 1977. A further series of test roofs installed in 1978 included <i>P. radiata</i> shingles pressure-treated with a copper naphthenate-based light organic solvent preservative. Evaluation of shingles in early 1984 showed that, although preservative leaching had occurred, the shingles appeared sound when examined under the microscope. Slight lichen growth was evident on some shingles. Untreated <i>P. radiata</i> shingles displayed marked fungal infection, early stages of decay and plentiful mold and lichen growth. Untreated <i>Thuja plicata</i> shingles, used as a reference, showed lichen and mold growth after seven years of exposure. -- AATA