The significance of serum SCC antigen as a tumor marker was investigated in 94 women with squamous cell carcinoma of the vulva. The incidence of elevated serum SCC levels varied from 10% in FIGO stage I to 40% in FIGO stage IV. We did not observe a correlation between elevated pretreatment SCC values and the presence of lymph node metastases. During follow-up, elevated serum SCC values were observed in 8 of 19 patients (42%) with recurrent or progressive disease. It is concluded that the determination of serum SCC levels does not provide additional information in the staging of squamous cell vulvar carcinoma, but can be useful for the early detection of recurrent disease during follow-up in some patients. However, elevated serum SCC levels were also found in 25% of patients without demonstrable tumor activity during follow-up and benign skin disorders were recognized as a cause of false-positive SCC results.