The biocatalytic oxidative tandem decarboxylation of C7–C18 dicarboxylic acids to terminal C5–C16 dienes was catalyzed by the P450 monooxygenase OleT with conversions up to 29 % for 1,11-dodecadiene (0.49 g L–1). The sequential nature of the cascade was proven by the fact that decarboxylation of intermediate C6–C11 ω-alkenoic acids and heptanedioic acid exclusively gave nonconjugated 1,4-pentadiene;