The stearoyl-acyl carrier protein desaturase (SAD) is a key enzyme that determines the ratio of saturated to unsaturated fatty acids in higher plants. Using reverse transcriptase polymerase chain reaction and rapid amplification of cDNA ends, a full-length cDNA of SAD was obtained from developing leaves of Cinnamomum longepaniculatum. Sequence analysis showed that the deduced amino acid sequence had high similarity to other reported SADs. The CSAD gene was functionally expressed in Escherichia coli, and the desaturating activity of the recombinant protein was markedly detected when assayed in vitro by adding spinach ferredoxin. Southern blot analysis indicated that the gene was a member of a small gene family. Northern blotting revealed that the CSAD gene was highly expressed in developing leaves of C. longepaniculatum. These results would provide opportunities for modifying fatty acid composition in C. longepaniculatum.