Amorpha-4,11-diene synthase (ADS) of Artemisia annua L. is a sesquiterpene cyclase that catalyzes the conversion of farnesyl diphosphate into amorpha-4,11-diene in the biosynthesis of the antimalarial artemisinin. To explore the mechanisms regulating the tissue-specific and developmental distributions of ADS, a full ADS promoter was generated using PCR, and fused to GUS for introduction into Arabidopsis thaliana. ADSpro::GUS fusion transcripts were organ-specific, mainly present in the anthers and trichomes of the green tissues of the juvenile leaves. This result was consistent with the ADS transcription pattern observed in A. annua as examined by RT-PCR. To determine the subcellular localization of ADS, an open reading frame (ORF) of ADS was fused to the green fluorescent protein (smGFP) gene and introduced into the A. thaliana protoplasts. GFP fluorescence was located exclusively in the cytosol, an indication that ADS is a cytosol-localized protein.