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Fractionated microneedle radiofrequency (RF) devices have been reported to be effective in treatment of various dermatologic disorders.To analyze histometric changes in skin-RF interactions using a fractionated microneedle delivery system.RF energies were delivered using a fractionated microneedle device to an in vivo minipig model with penetration depths of 0.5, 1.0, 1.5, 2.0, 2.5, and 3.5 mm; RF conduction times of 20, 50, 100, and 1,000 ms; and energy levels of 5.0, 10.0, 20.0, 25.0, 37.5, and 50.0 V.Immediately after treatment, skin samples showed that the RF-induced coagulated columns in the dermis formed a cocoon-shaped zone of sublative thermal injury. Four days after the treatment, skin specimens demonstrated reepithelialization, and the dermal RF-induced coagulated columns showed mixed cellular infiltration, neovascularization, and granulation tissue formation. Microneedle depth and RF conduction times, but not energy level, significantly affected histometric values of RF-induced dermal coagulation. Microneedle RF treatment affected adnexal structures by coagulating follicular epithelium and perifollicular structures.Our data may be of use as an essential reference for choosing RF parameters in treatment of various skin conditions.