The aim of this study was to investigate the regulation and clinical significance of serum acute phase proteins. The patients were divided into three groups: group I consisted of 11 patients with less than 20% of TBSA; group II 10 patients with 20-50% of TBSA and group III 11 patients with more than 50% of TBSA. Blood samples were taken at 8, 24, 48 and 72 h postburn, and in group III additional blood samples were taken on the 7th, 14th, 21st day or in septic episode. The concentration of CRP and C3, Tf, PA were detected by rate nephelometry, agar immunodiffusion and rocket immunoelectrophoresis respectively. Compared with controls, the peak value of CRP was observed during 48-72 h (P < 0.01), C3 decreased at 8 h and lowest at 24 h. Tf was lowered at 48 h, PA and Tf shared the similar changes. However, all four variables had no marked difference during infection and sepsis. The results showed no correlation between C3 and CRP (r = 0.0885, P > 0.05). The results suggested that: 1. CRP mainly reflected the extent of injury but not sepsis; 2. increased CRP was not the causative factor of decreased C3. Tf reduction accelerated bacterial growth.