The effect of fungal elicitor, derived from mycelial extracts of Fusarium conglutinans, on thiophene production in hairy-root cultures of Tagetes patula was studied. Various concentrations of elicitor were added to the culture media. Time-course experiments were carried out using a defined concentration of elicitor. Thiophene production increased with the addition of elicitor. The major thiophenes produced were 5-(4-acetoxy-1-butenyl)-2,2'-bithiophene and 5-(buten-1-enyl)-2,2'-bithiophene.