Prognostic relevance of serum p53 antibodies was assessed in 96 patients with microscopically proven small cell lung cancer (SCLC). The study group included 67 males and 29 females; mean age 58 years; range 35--86 years; 60 with limited disease (LD), and 36 with extensive disease (ED). The control group consisted of 41 patients with non-malignant diseases. The presence of p53 antibodies was assayed by the immunoenzymatic method (P53 ELISA kit, PharmaCell, France). Antibodies were present in 26 SCLC cases (27%); 15 (25%) in LD and 11 (31%) in ED. Antibodies were also found in one out of 41 control subjects (2%). There was no correlation between the level of antibodies and clinical characteristics of SCLC patients including age, gender and extent of disease. The median follow-up for the entire group was 30 months (range: 11--39 months). By the time of analysis, 78 patients (82%) had deceased. Median survival in SCLC patients with and without antibodies was 42 and 39 weeks, respectively (log rank, P=0.81). These results indicate the lack of clinical relevance of serum p53 antibodies in SCLC.