Piroxicam, a non-steroidal anti-inflammatory agent, was administered in the feed to rats which had been inoculated intra-rectally with N-methylnitrosourea (MNU). When examined 5 months later, the piroxicam-treated rats had a significant reduction of intestinal tumors compared to tumor incidences and tumor numbers in rats which were fed drug-free diet. There was no evidence of toxicity associated with the consumption of piroxicam.