Desiccation resistance is important for the survival of adult insects, although this key physiological trait has rarely been studied in tephritid flies. In the present study, desiccation resistance of female and male adult Queensland fruit flies Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) is determined with respect to age after adult eclosion. Resistance to acute starvation is measured over the same period to disentangle the competing roles of water loss and food deprivation. Survival of adult B. tryoni subjected to conditions of low humidity and starvation is reduced considerably compared with adults that are subjected to starvation alone. Desiccation resistance of adult female B. tryoni is generally lower than that of adult males. Desiccation resistance of adult B. tryoni declines in a continuous and regular manner over the first 20 days after adult eclosion. The regular pattern of declining resistance to desiccation with age in B. tryoni indicates that this reduction is not associated with the onset of maturity and maintenance of reproductive structures, nor with sexual activity. By contrast, resistance to starvation is similar at 0 and 6 days after adult eclosion, and declines thereafter. Survival under starvation and water stress is not related to wing length, which is a standard measure of fly size.