The oil contents in seeds of Brachychiton discolor, Brachychiton diversifolius, and Brachychiton acerifolius (Sterculiaceae) were 29.3, 32.1, and 30.5%, respectively. Linoleic and oleic acids were the predominant fatty acids in the triacylglycerols. Cyclopropene fatty acids, malvalic and sterculic, were present in small concentrations (4.6-5.6%, 0.7-1.1%). The protein contents of the three seeds were 26.9, 38.1, and 35.0%, respectively. Amino acid analysis showed that the proteins contained nutritionally useful quantities of most of the essential amino acids except for those containing sulfur. Cyclopropene fatty acids (CPFA) are constituents of seed oils in the botanical families Sterculiaceae, Malvaceae, and Bombacaceae (Smith, 1970), which have been shown in animal feeding trials to have adverse biological effects (Phelps et al., 1965; Lee et al., 1971). However, seeds of one Brachychiton species, Brachychiton diversifolius, are indigenous food eaten by Australian Aborigines (James and Forbes-Ewan, 1982). This paper reports for the first time the fatty acid and amino acid compositions of B. diversifolius, Brachychiton discolor, and Brachychiton acerifolius seeds.