In common with pine plantations established in different parts of the Australian Continent, certain sections of those planted by the Forests Department of Western Australia in the South-West of that State have developed “sick areas,” in connection with which plant pathologists and entomologists have failed to associate any causative organisms. Attention has been given to the possibility of the primary causes of such unsatisfactory growth being attributable to soils being deficient in one or more plant nutrients essential to the growth of the pine crop, and the results of a large number of investigations and experiments along these lines are given. Various unhealthy conditions of P. radiata and P. pinaster are described and attention is drawn to the desirability of standardising names for these conditions. A relation has been established between soil types and pine growth. Chemical analyses have shown that the soils of the majority of plantation sites available are low in plant nutrients according to recognised agricultural standards. The stunting of pines in new nurseries has been overcome by applying a dressing of soil taken from old pines or alternatively spreading fruiting bodies of Rhizopogon luteolus on the area to be used as a nursery. Ash analyses have been made of wood, bark and needles from healthy and unhealthy plants. For some unexplained reason, the figures for Soda (Na2O) were the only ones appearing to have any significance. A study of the nitrogen cycle of soils from virgin eucalypt forest, ploughed land, and plantations showing good and poor growth gave no significant differences. In common with agriculture, remarkable results have been obtained with superphosphate, but Calcium, Nitrogen and Potash have not increased the responses obtained with water-soluble phosphate. Among the experiments carried out to try and ascertain the cause of “rosetting” in young pines was an experiment consisting of spraying the small pines with chemically pure solutions of eight minor elements. Immediate and striking response occurred in colour, length of needle and restoration of normal growth on pines sprayed with Zinc chloride. A parallel series of experiments involving pouring quantities of the same solutions around the roots of the young pines has not given equally rapid and striking results. Other factors discussed are soil changes arising from pasture development prior to planting; cultivation of the planting site; the effect of clearing methods adopted; and the varying reactions to site of different species of pine.