A few researchers have reported that major depression may be associated with higher levels of positive acute phase proteins(APPs), such as haptoglobin(Hp), ${alpha}1$-antitrypsin(${alpha}1AT$), ceruloplasmin(Cp) and lower levels of negative APPs(visceral proteins), such as albumin(Alb) and transferrin(Tf). Elevated levels of positive APPs and a drop in negative APPs constitute important indicators of immune activation. This study was designed to investigate whether altered serum concentrations of positive APPs and of negative APPs reflect the state of depression. Twenty patients who fulfilled DSM-III-R criteria for major depressive disorder and for dysthymic disorder and twelve normal healthy controls were included. The authors measured positive APPs(Hp, ${alpha}1AT$, Cp) and negative APPs(Alb, Tf) using rate nephelometry and bromcresol green method. 1) There were significant increases of ${alpha}1AT$, Cp in major depressed patients as compared with normal controls. Trends towards higher Hp and lower Alb, Tf in major depressed patients were observed. 2) No significant difference of APPs concentrations between dysthymic patients and normal controls was found. 3) Severity of depression(HDRS, BDI score) was related to Hp, Cp, ${alpha}1AT$ value positively. Our findings are partially compatible with the hypothesis that major depression may be accompanied by acute phase response with higher levels of positive APPs and lower levels of negative APPs.