Reliable synthetic routes to isotopically labelled dimethyl [13C,2H]diallylmalonates (1) have been developed. Dimethyl diallylmalonates readily undergo transition-metal catalysed cycloisomerisation and the isotopically labelled substrates are expected to be of general utility in the study of the mechanism of such reactions. In the synthetic routes developed, the 2H labelled allyl chains were introduced by reduction of propargyl functionality with Schwartz reagent. The regio- and stereo-selectivity of such reactions allowing highly selective labelling strategies. The 13C labelled allyl chains were introduced via Pd-catalysed allylic alkylation of 13C- or 2H-labelled dimethyl allylmalonate anions using [3-13C1]allyl benzoate as the allylic electrophile. Using these methods, dimethyl [1,7-(E,E)-2H2]hept-1,6-dienyl-4,4-dicarboxylate (5), dimethyl [2,6-2H2]hept-1,6-dienyl-4,4-dicarboxylate (6), dimethyl [1,7-(Z,Z)-2H2]hept-1,6-dienyl-4,4-dicarboxylate (7), dimethyl [1,1,2,6,7,7-2H6]hept-1,6-dienyl-4,4-dicarboxylate (8), dimethyl [1,3-13C1,5,7-13C1]hept-1,6-dienyl-4,4-dicarboxylate (9), dimethyl [1,3-13C1,6-2H1]hept-1,6-dienyl-4,4-dicarboxylate (10), and dimethyl [1,3-13C1,7-(E)-2H1]hept-1,6-dienyl-4,4-dicarboxylate (11) have been prepared.