Since we described the quantitative detection of free tumour cells in peritoneal washes (Nakanishi et al, 2000) and its prognostic significance for gastric cancer patients (Kodera et al, 2002), many investigators have reported the usefulness of quantitative CEA mRNA detection in retrospective risk assessments of peritoneal recurrence (Nakanishi et al, 2004). The gene discussed is CEACAM5; the disease is gastric cancer.