A mouse feeder in common use in the US was modified to eliminate spillage, contamination by excreta and formation of food aggregates. The improved feeder consists of a glass jar which holds 100 g of meal-type feed, an inner metal mesh tube, a marble placed inside the inner mesh tube, and a snap-on metal lid. Female mice [B6C3F1 and CD-1(ICR)] were housed 5 animals/cage. Only slight contamination by feces, but not by urine, was observed in a 13-week feeding study with Japanese meal-type food and the improved feeder. Food spillage also decreased. Food consumption was significantly higher in cages with the conventional Japanese feeder than in the improved one, but no difference was observed between the two feeders in body weight gain.