p53 tumour suppressor gene alterations are one of the most frequent genetic events in lung cancer. A subset of patients with p53 mutation and cancer exhibited circulating serum anti-p53 self-antibodies (p53-Ab). The prevalence of these antibodies in lung cancer is currently being analysed in a multicentric study. In a group of homogeneous SCLC patients, p53-Ab were detected in 20/97 (20.6%) individuals. In this group of patients, Cox's multivariate analysis identified disease extent (p = 0.022), WHO initial performance status greater than 0 (p = 0.005), and the absence of a complete response after 6 months of treatment (p < 0.0001) as independent prognostic variables, with p53-Ab being of borderline significance (p = 0.051). In the subset of limited-stage SCLC patients, Cox's multivariate analysis found p53-Ab (p = 0.033), WHO initial performance status greater than 0 (p = 0.028), and absence of a complete response (p < 0.001) to be independent prognostic variables. Thus, actuarial analysis showed that patients with limited-stage SCLC and p53-Ab had a median survival time of 10 months, whereas limited-stage SCLC patients without p53-Ab had a 17-month median survival time (p = 0.014).Therefore, serum assay of p53-Ab could help to identify a population of SCLC patients with an especially poor prognosis. This population could represent patients with tumours harboring aggressive p53 mutations.