Rust-spot on North American ginseng roots (Panax quinquefolius L.) is considered a physiological, not a pathological disorder. Ginseng rust-spot starts as an orange spot on the surface of the root and may spread forming a sunken, round to irregular lesion. 5 mm in diameter. Pieces of root, 7 mm in length and containing a rust-spotted lesion, were embedded in agar and sectioned using a vibratome. These sections and hand sections, cut with a two-sided razor blade, were examined using fluorescence microscopy. The 4-5 cell layers of the periderm were destroyed in the area of the lesion and orange substance:, were deposited in and around the lesion. Sections stained with vanillin-HCI and viewed using bright field microscopy confirmed that the orange substances were phenolic compounds. Scanning electron micros-copy showed that the periderm had pulled away from the root, or was completely destroyed, in the area of the lesion. The smooth surface of the lesion indicates the deposition of phenolic compounds in surrounding cells as a wound response. Roots sprayed or dipped in ethephon (1500 mgㆍL$^{-1}$ ) developed rust-spots, more so at 21$pm$2$^{circ}C$ than at 3$pm$0.2$^{circ}C$. Roots held at 21$pm$2$^{circ}C$ were yellowish and developed white cell proliferations. Comparable control roots also developed rust-spots likely due to the high undecomposed organic matter content of the incubation soilless mix.