Phosphatidylcholine (PPC) and sodium deoxycholate (DC) injections have been used cosmetically to reduce localized fat, but to date, few studies have addressed the histological effect of human fat tissue following injections of PPC and DC. We injected PPC and DC mixed with normal saline into the patient's abdominal area. Examinations of postinjection tissue revealed marked changes within the subcutaneous fat. We observed important microscopic evidence of substitution of fat by fibrosis, marked inflammatory infiltration with microabscess formation in the dermis, and septal and lobular panniculitis with thick fibrous septa. Fat necrosis with microcalcification and cyst formation were observed in the subcutaneous fat. Fibroid necrosis with extravasation was noted in the small vessels around fat necrosis. Therefore, careful use of PPC and DC is recommended when patients want to cosmetically reduce localized fat.