Technical Abstract: Traditional plant breeding is often limited by the genetic diversity within a species. The use of biotechnology allows introducing into a plant, specific traits that come from the same or another plant species. In this paper, we focus on tissue culture of sunflower (Helianthus annus L., Asteraceae), particularly related to rooting transgenic sunflower plantlets. Prior to 1985 there had only been four reports of successful regeneration of sunflower plants in tissue culture. Although this report is more than 20 years old, sunflower continues to be a challenging species in tissue culture including rooting. The objective of our study was to compare agar and liquid media for rooting transgenic sunflower plantlets. Sunflower plantlets grown in peat pellets are less likely to become vitrified and more likely to develop to maturity.