Early in April 1976, small sunflower plants showing symptoms of rust infection were submitted for identification from the Biloela district in central Queensland. The affected plants were in a parental line of an experimental hybrid resistant to Puccinia helianthi Schw. Pustules formed on the R line, while on the A line only chlorotic spots up to about 3mm diameter were seen. Fungal morphology was indistinguishable from that of P. xanthii Schw., and inoculation of Xanthium pungens in the glasshouse with inoculum from sunflower resulted in numerous infections. This observation extends a previous report (1) where susceptibility of sunflower to P. xanthii under glasshouse conditions was recorded. The susceptible parental line is not yet in commercial use, and other lines in the same plots were not affected by P. xanthii (Pacific Seeds, pers. comm.). The range of reactions in sunflower varieties and breeding lines will be tested further in the glasshouse.