The study was conducted to induce the hairy roots of Paramignya trimera by using Agrobacterium rhizogenes K599 and investigate some factors affecting the growth of hairy roots. Three types of materials (calluses, cotyledons and in vivo roots) have been used as sources for hairy roots induction. The study results showed that, the in vivo roots was the most suitable material to induce the hairy roots. It was suggested that roots of the seedlings soaked in A. rhizogenes K599 suspension at the cell density of OD₆₀₀=0.6 for 30 minutes yielded the highest rate of root induction (42.7%). The hairy roots grew rapidly and stably when cultured in WPM/2 medium without phytohormones supplement in dark conditions for 6 days. Illumination with white fluorescent light was found to inhibit hairy root formation during co-cultivation period but promote it during the bacterial elimination step. The transgenic hairy root lines were confirmed by polymerase chain reaction (PCR) using rolC specific primers.