We investigated the influence of jasmonic acid (JA) in combination with other growth substances upon the mycorrhizal fungus Suillus variegatus. JA was added alone or in combination with kinetin (KIN), gibberellic acid (GA), indole acetic acid (IAA) and abscisic acid (ABA) to the MMN nutrient medium in concentrations of 0.1 - 100 μg/l. Fresh weight of mycelia was measured after 17 days of growth. JA is a strong inhibitor of the growth of mycorrhizal fungi, even at the lowest concentrations, nevertheless, it is only a partial inhibitor in the presence of stimulators. The growth of mycelium is dependent on the specific combination of all growth regulators, present in the roots or the root exudate. © 1990.