A study was undertaken to determine the effects of Enokitake {Flammulina velutipes) on the growth and intestinal micro flora of rats. Male Wistar rats (6 weeks of age; body weight 113 g) were fed either a control diet or an experimental diet containing 5 % Enokitake powder for 104 days. The following results were obtained: 1) The body weight of the Enokitake group had was increased significantly at 7 to 43 days and also at 63 days. From 70 days on, there was no difference between the Enokitake group and the control group. A significant decrease was observed in the growth ratio of the Enokitake group from 7 to 78 days. 2) There was a significant decrease in total feed intake for the Enokitake group from 7 to 78 days. Feed efficiency and protein efficiency ratio were decreased significantly on days0 to 7, 0 to 14, 0 to 28 and 0 to 42 days. On days 0 to 7 and 0 to 14, energy efficiency ratio was decreased significantly. 3) The Enokitake group was significantly low with apparent nitrogen digestively, apparent nitrogen retention and also nitrogen balance at 7 to 14 days. The Enokitake group was significantly high with apparent nitrogen retention on days 28 to 35. 4) In the Enokitake group, the cecum weight per carcass weight (%) increased significantly, but retroperitoneal fat tissue weight, small intestine and colon per carcass weight (%) decreased significantly. The Enokitake group showed a tendency for the length of the small intestine to increase. 5) The fatty acid composition of the retroperineal fat tissues and linolenic acid was increased significantly, while palmtic acid decreased significantly. In the fatty acid composition of the liver, linolenic acid was significantly high. 6) There were no differences between the Enokitake group and the control group in content of the protein and the lipid included into the liver. 7) Total Lactobacillus spp. increased in the Cecum.