The biological performance of copper-chrome-arsenic (Cu-Cr-As, CCA) was compared with its distribution between lignin and wood carbohydrates of <i>Pinus patula</i> and <i>Eucalyptus grandis</i> under different test conditions. Increasing CCA percentage on holocellulose was correlated with increasing timber durability and decreasing degree of attack by fungi and termites. Small changes in treatment conditions led to improved performance, or equal performance at lower retentions, of the usual CCA formulations with <i>P. patula</i> but not with <i>E. grandis</i>. More effective CCA formulations for hardwoods are proposed and their advantages and disadvantages discussed. Interference from tannins is taken into account. A new theory reconciles the lignin, microdistribution and other theories of soft-rot attack as different facets of the same phenomenon, through a new common factor (deposited and structural flavonoid tannins). -- AATA