The poor prognosis of patients with gastric cancer with free abdominal tumour cells on cytological examination has been described in Japan. In a randomized trial in the Netherlands comparing D1 and D2 lymphadenectomy for gastric cancer, patients were subjected to cytological examination of abdominal washings on an optional basis; findings were of no consequence for scheduled treatment. Cytology results in 535 patients were obtained, in 457 (85.4 per cent) after curative resection and in 78 (14.6 per cent) after palliative operation. There was a clear association of positive cytology results with serosal invasion (12 per cent positive cytology) and lymph node infiltration (7.5 per cent positive cytology). Survival of those with positive cytology results was significantly lower than that of those with negative findings, irrespective of the procedure employed (curative or palliative). Cytological examination of abdominal washings increases the accuracy of staging and improves the selection of patients suitable for curative or palliative resection.