Trialkyltin alkoxides, R3SnOR′, can be prepared conveniently by thermal decarboxylation of a mixture of the oxide, (R3Sn)2O, and dialkyl carbonate, (R′O)2CO, or (except when R = Me or Et) by azeotropic dehydration of a mixture of the bistrialkyltin oxide and alcohol, R′OH. Under these latter conditions, dibutyltin oxide forms the 1,1,3,3-tetra-butyl-1,3-dialkoxydistannoxanes, (R′O)Bu2Sn·O·SnBu2(OR′), which (except when R = Me) decompose on distillation into the dialkoxide, Bu2Sn(OR′)2, and oxide, Bu2SnO. The temperature at which the n.m.r. coupling between tin atoms and the alkoxy-groups is broken in the alkoxides Bu3SnOR′ shows that the rate of exchange follows the sequence MeO > EtO > PhCH2·O > Me3C·CH2·O, Me2CH·O, PhMeCH·O, Ph2CH·O.