Retentions of CuO, CrO₃, and As₂O₅ were measured at 2.5 and 7.5 centimeters from the edge of each of 7 plies in samples of 12 millimeter-thick plywood panels soaked for 1, 3, 6, 12, or 24 hours in CCA. Retention of total oxide in the face and back plies (1+7) was greater than the total amount in the other plies. Retentions were in the following decreasing order: 1+7; 3+5 (cross plies); 2+6 (cross plies); 4 (core ply). Retention increased as treatment time increased. Total oxide retention of over 5 kg/m³ (New Zealand Timber Preservation Standard Specification) is attained at 1 hour for plies 1+7 and after 6 hours for 3+5. Relative penetration of Cu, Cr, and As was not affected by treatment time. At 7.5 centimeters from the edge amounts of Cu and Cr became disproportionate and resistance to leaching of CCA was lowered. After 6 hours soaking the proportion of active elements at 2.5 centimeters from the edge was consistent; at 7. 5 centimeters a soaking time of 24 hours was required for consistency. -- AATA