Despite the production of numerous flowers, poor fruit set and excessive premature fruit drop has been frequently reported to limit yield in cashew. The primary objective of this study was to identify factors limiting fruit set and yield in selected cashew cultivars grown in the Northern Territory. The phenology of flower opening, sex ratio, and percentage initial and final fruit set were determined in five cultivars. Two phases of flower opening were observed, an initial mixed phase, with both male and hermaphrodite flowers, followed by a male dominant phase. A mean of 607.5 flowers were produced per panicle, of which 53.5 (8.8%) were hermaphrodite. Mean initial fruit set of 22.2 and final fruit set of 5.9 per panicle was observed, representing 41.5% and 11.0% of the hermaphrodite flowers, respectively. A study on the pattern of flower and fruit abscission in two cultivars revealed that 84.5% of the total number of hermaphrodite flowers produced abscised prior to fruit maturity. A mean of 30.3% aborted at the flower stage, 47.9% abscised when fruits were small (nut length less than 10 mm) and 6.3% dropped when the nuts had attained a size greater than 10 mm in length. Pollination experiments were performed to determine the period of pistil receptivity, the timing of pollen tube growth and the extent of self and cross compatibility in selected cultivars. Pollen germination on the stigma decreased when pollination was delayed beyond anthesis. Pollen tube entry into the ovule, and initial and final fruit set were significantly reduced when pollination was delayed until 6 hours after anthesis. Pollen tube growth in the receptive pistil was rapid, with a pollen tube present in the ovary and the ovule within 6 and 12 hours of pollination, respectively. No pollen-pistil incompatibility was observed in cashew, with no difference in the percentage of pistils with a pollen tube entering the ovule between self and cross pollination. Initial and final fruit set were not significantly affected by pollen source, suggesting that both pre- and postzygotic incompatibility mechanisms were not operating amongst the selected cultivars. Studies on post-pollination events in the cashew flower were carried out to identify possible causes of the high rate of premature abscission during early fruit development. Pollen tube inhibition was observed in the style of both self and cross pollinated flowers. Arrested tubes showed distinctive morphological features including, swollen tips, twisting, and irregular callose deposition. The first sign of fertilisation, the formation of nuclear endosperm, was observed 3 to 4 days after pollination. The first division of the zygote became apparent 10 to 12 days after pollination when the nut was around IO mm in length. Fruit drop was highest at this stage of development. The translocation of 14C-labelled assimilates during panicle and fruit development indicated that reproductive organs are a strong sink for photosynthates, even in the presence of other competing organs, such as developing leaves and roots. During the early stage of panicle development, 47.5% of the 14C-activity exported from the fed leaf was detected in the reproductive organs, increasing to 79.8% when flowering had commenced in the fully developed panicle. The amount of 14C-activity, as a percentage of the total radioactivity exported from the fed leaf detected in the fruits increased during development, with 4.4% and 90.2% present following 14CO2-feeding 1 and 48 day/s after the last hand pollination. In the absence of fruits, 70.2% of the 14C-photosynthate exported from the fed leaf was detected in the lower stem and roots of potted plants, compared with 1.1% when fruits were present. The timing of pollination and competition for assimilates were identified as factors which may limit fruit set and yield in cashew. Pollination should occur within 6 hours after anthesis for optimum fertility in terms of pollen tube growth, fruit set and retention. Pollinator activity is required, particularly during peak hermaphrodite flowering to ensure successful pollination and the provision of beehives may be necessary in some orchards. Competition for assimilates, particularly between developing fruits may be responsible for the high rates of fruit drop at the early stages of development. However, further work on increasing assimilate supply to developing fruits is required before any management practices can be recommended.