Two Cases of Tick Bites Caused by Ixodes Nipponensis -Scanning electron microscopic study- Nam Joon Cho,M.D.,Dong Sik Ban, M.D., Bailk Kee Cho, M.D*., Young Jin Oh,M.D.,* Won Koo Lee, Ph.D.** Department of Dermatology, Yonsei University College of Medicine, Seoul, Korea Department of Dermatology, Catholic University Medical College*, Seoul, Korea Department of Biology, College of Science, Chonbuk National University**, Chonju, Korea We report two cases of tick bites caused by Ixodes nipponensis. One patient was a 10-month-old female who developed a protruding mass and tiny bleeding on forehead for about one week. The other was a 5-year-old female who had had a tick on occipital area for an unknown period. A excision biopsy specimen from the skin lesion of the latter case showed mild inflammatory cells in the dermis and dense inflammatory cells mainly composed of neutrophils in the subcutaneous fat. The two ticks were identificated as Ixodes nipponensis by scanning electron microscopic study. (Kor J Dermatol 29(4) : 533-537, 1991)