Abstract: 3,7-Dimethyl-2,6-octadien-1-al of formula I is prepared continuously by: thermally cleaving, in the presence or absence of an acid catalyst, 3-methyl-2-buten-1-al diprenyl acetal of formula II: thereby eliminating 3-methyl-2-buten-1-ol of formula III and yielding cis/trans-prenyl 3-methylbutadienyl ether of formula IV: thermally rearranging the resultant butadienyl ether of formula IV thereby yielding 2,4,4-trimethyl-3-formyl-1,5-hexadiene of formula V: subsequently rearranging intermediate (V) thereby yielding citral product of formula I, which comprises: as the reaction proceeds, continuously distilling the reaction mixture thereby continuously removing prenol, which is formed by degradation of acetal II, and the intermediates of formula IV and V and any citral product which is formed during the reaction; and thermally rearranging said intermediates of formula IV and V at a temperature of 100-200° C.