Plasma concentrations of soluble tumor necrosis factor α(TNF-α) receptor type I (sTNF-RI) were assessed in two complex regional pain syndrome (CRPS) patient groups (n = 30 and n = 16) and healthy controls (n = 25). Patients with CRPS and mechanical hyperalgesia had higher levels of sTNF-RI (1,661.8 ±146.8 pg/mL) compared with those with CRPS with identical clinical appearance but without hyperalgesia (1,155.9±56.3 pg/mL) and controls (1,239.5 ±42.9 pg/mL). This study suggests involvement of TNF-αin mechanical hyperalgesia of CRPS. Plasma concentrations of soluble tumor necrosis factor α (TNF-α) receptor type I (sTNF-RI) were assessed in two complex regional pain syndrome (CRPS) patient groups (n = 30 and n = 16) and healthy controls ) With CRPS and mechanical hyperalgesia had higher levels of sTNF-RI (1,661.8 ± 146.8 pg / mL) compared with those with CRPS with identical clinical appearance but without hyperalgesia (1,155.9 ± 56.3 pg / mL) and controls (1,239.5 ± 42.9 pg / mL). This study shows involvement of TNF-αin mechanical hyperalgesia of CRPS.