The serum levels of lactoferrin (LF), α1-antitrypsin (α1-AT), α2-macroglobulin (α2-MG), and its immune complex with IgG (α2-MG-IgG) were studied in patients with mild and severe psoriasis (PS) and in those with atopic dermatitis (AD) before and after treatment to establish their possible role in the pathogenesis of the diseases and their diagnostic or prognostic value. It was ascertained that the levels of α2-MG were decreased and those of LF and α2-MG-IgG were increased in severe PS (there was a rise in LF only in mild PS). In AD, the circulating concentrations of α1-AT, α2-MG, and α2-MG-IgG were elevated regardless of the severity of the process. Standard treatment led to the relief of symptoms in 25-30% of the patients with severe disease forms and in 60-70% of those with mild PD or AD; however, it had, in the average, no substantial impact on the serum indicators under study. The abnormal pretreatment concentrations of the indicators in question were observed in 20-80% of the patients depending on the indicator. Of them, treatment-induced levels were normalized in no more than 68% (not more 11% according to some parameters). The substantial change in the levels of immunoregulatory α2-MG and LF even in the total circulatory system in the examined skin disease suggests that they are actively involved in the pathogenesis of the diseases. A reasonably high individual variability in the indicators prior to and particularly following the therapy performed suggests that they may be used as additional prognostic criteria for the course of a disease (a shorter remission and a high probability of disease progression may be surmised even in case of alleviated cutaneous manifestations during treatment without substantially changing the levels of LF, α1-AT, α2-MG, and α2-MG-IgG in severe PS and in AD).