This study investigates the clinical utility of squamous cell carcinoma antigen (SCC-Ag), circulating immune complexes (CIC), and immunoglobulins (IgA, IgG, IgM) in the diagnosis, monitoring, and prognosis of 117 squamous cell carcinoma of the head and neck (SCC-HN) patients having local and/or systemic treatment. Serum marker levels were measured in a prospective study. SCC-Ag was positive in 28.2% of patients, the CIC in 63.2%, the IgA in 11.1%, the IgG in 15.4%, and the IgM in 9.44%. Statistically significant correlation was found between the initial SCC-Ag levels and tumor localization, whereas the CIC levels were increasing significantly with progressing disease stages. It was also found that the significant decrease of SCC-Ag, IgA, and CIC levels at the end of treatment was correlated with an increased incidence of disease-free status. The initial values of IgG and the disease stage were significantly correlated with a favorable treatment outcome. The pretreatment elevated SCC-Ag and IgM serum values showed a significant trend to predict a disease progression. Using a Cox proportional hazards model the IgG serum values, the primary site, and the disease stage were significant predictors for time to progression. The significant decrease of SCC-Ag, IgA, and CIC values at the completion of treatment was correlated with an increased incidence of disease-free status. This study indicates that only the estimation of SCC-Ag and in some degree the IgM and/or IgG is a potential tool for monitoring the efficacy of treatment or disease recurrence in SCC-HN.