TLC densitometry was developed for the detection of plant materials which potentially contain plumbagin such as the whole plants and cell suspension culture of Plumbago zeylanica. Callus and cell suspension cultures of P.zeylanica were successfully established from young leaf explants. The culture medium used for both callus induction and maintaining the cell suspension cultures was LS containing with 0.2 mg/l 2, 4-D and 30 g/l sucrose. To verify the optimum culture conditions for plumbagin production, cell suspension cultures were tested by changing the various basal media, plant growth regulators and carbon source. The cell suspension culture produced more plumbagin in MS medium, in the presence of 2, 4-D or BA as a growth regulator and manitol as a carbon source. For the whole plants of P.zeylanica were obtained from Minburi Bangkok. The analysis revealed that plumbagin was present in every part of plant, especially in the roots. The plumbagin content in the roots were 0.226%, stem 0.089%, mature leaves 0.010-0.030%, young leaves 0.014% and flowers 0.002%, on the dry weight basis. Apparently, this is the first report on the formation of plumbagin in P.zeylanica cell suspension cultures and the quantitative distribution of plumbagin in the whole plant.