A simple, rapid analytical method for the quantitative determination of nine neo-clerodane diterpenoids was developed. The neo-clerodane diterpenoids present in the plant material and extracts were separated with an acetonitrile-water gradient at a flow rate of 1 mL per minute. The HPLC separation was performed on a Phenomenex Luna C18(2) (150 x 4.6 mm I.D., particle size 5 microm) reversed phase column with detection at 220 nm. The limit of detection was 0.24-0.90 microg/mL. The relative standard deviation (RSD) values for the determination of neo-clerodane diterpenoids in plant extracts were less than 3.20%. This is the first analytical method developed for qualitative and quantitative analysis of nine neo-clerodane diterpenoids by HPLC with PDA detection.