Artemisinin is a sesquiterpene antimalarial compound produced, though at low levels (0.1-1% dry weight), in Artemisia annua in which it accumulates in the glandular trichomes of the plant. Due to its antimalarial properties and short supply, efforts are being made to improve our understanding of artemisinin biosynthesis and its production. Native beta-cyclodextrins, as well as the chemically modified heptakis(2,6-di-O-methyl)-beta-cyclodextrin (DIMEB) and 2-hydroxypropyl-beta-cyclodextrins, were added to the culture medium of A. annua suspension cultures, and their effects on artemisinin production were analysed. The effects of a joint cyclodextrin and methyl jasmonate treatment were also investigated. Fifty millimolar DIMEB, as well as a combination of 50 mM DIMEB and 100 mu M methyl jasmonate, was highly effective in increasing the artemisinin levels in the culture medium. The observed artemisinin level (27 mu mol g(-1) dry weight) was about 300-fold higher than that observed in untreated suspensions. The influence of beta-cyclodextrins and methyl jasmonate on the expression of artemisinin biosynthetic genes was also investigated.