The methyl- and the dimethyl-dibenzofurans having both methyl groups in the same ring have been synthesised and their spectra recorded. Degradative work on rhodomyrtoxin, the toxic principle of the immature Australian finger cherry (Rhodomyrtus macrocarpa Benth.), gave a compound which was probably a dimethyldibenzofuran having both methyl groups in the same ring. In order to identify this, the six possible dimethyldibenzofurans and the four methyldibenzofurans have been synthesised, and their ultraviolet and infrared spectra recorded. The general method adopted was essentially that of Ebel: 2-Bromocyclohexanone with a sodium phenoxide gave a keto-ether which, on treatment with concentrated sulphuric acid or polyphosphoric acid, cyclised to a 1:2:3:4-tetrahydrodibenzofuran. This, upon dehydrogenation with palladium-charcoal at 230°, gave a dibenzofuran in good yield. The synthesis of 2- and 4-methyldibenzofuran and of 1:3-, 2:3-, 3:4-, 1:4-, and 2:4-dimethyldibenzofuran by this method was straightforward and unambiguous. For the synthesis of 1- and 3-methyldibenzofuran, and of 1:2-dimethyldibenzofuran, the methyl groups were introduced in the cyclohexanone part of the molecule. The ultraviolet and infrared spectra of the methyl- and dimethyl-dibenzofurans are reported; in general, the infrared spectra are dominated by a sharp strong band in the 8.3-8.4 μm region which can be used for the identification of alkyldibenzofurans.