Winter soil application of paclobutrazol to very high density four year old peach and nectarine plantings (20,000 trees/ha) increased fruit yields up to 40%, but reduced fruit size by 20 to 30% due to increased fruit numbers (64%) retained on trees. Detailed studies on the nectarine cultivar Fantasia showed that PP333 resulted in a marked reduction in vegetative growth, decreasing tree height (45 to 47%) and leaf size (77%). Fruit from the treated trees had enhanced colour, sugar levels, and shelf life during storage. At the lowest rate of PP333 (28mg a.i./tree) fruit maturity was delayed whilst at higher rates (83 and 250mg a.i./tree) maturity was brought foreward. This experiment confirms the effect of paclobutrazol as a useful management tool for stonefruit production systems. PP333 can be used by the grower to achieve management of tree size, greater fruit retention, enhanced quality and manipulation of maturity and storeability.