BACKGROUND Adenocarcinomas of the rectum shed viable cells, which have the ability to implant. Intraoperative rectal washout decreases the amount and viability of these cells, but there is no conclusive evidence of the effect of rectal washout on local recurrence after rectal cancer surgery. METHODS Data were analysed from a population-based registry of patients who had anterior resection from 1995 to 2002 and were followed for 5 years. Rectal washout was performed at the discretion of the surgeon. National inclusion of patients with rectal cancer and follow-up was near complete (approximately 97 and 98 per cent respectively). RESULTS A total of 4677 patients were analysed (3749 who had washout, 851 no washout and 77 with information missing); 52.0 per cent of patients in the washout group and 41.4 per cent in the no-washout group had preoperative radiotherapy (P < 0.001). Local recurrence rates were 6.0 and 10.2 per cent respectively (P < 0.001). Univariable and multivariable logistic regression analyses produced odds ratios that favoured washout: 0.56 (95 per cent confidence interval (c.i.) 0.43 to 0.72) and 0.61 (0.46 to 0.80) respectively (both P < 0.001). In multivariable analysis restricted to patients who had curative surgery, the odds ratio was 0.59 (95 per cent c.i. 0.44 to 0.78; P < 0.001). CONCLUSIONS There was a more favourable outcome in patients after rectal washout than without.