Previous studies have suggested that a cereal- and milk-free diet may be beneficial to schizophrenics and that the gluten in regular diets is harmful to schizophrenics. In an effort to replicate these findings, with improved control vehicles, patients on a locked ward were placed on a cereal- and milk-free diet. Thirteen schizophrenics were given gluten-free peanut-flour supplementary cookies and 13 were given virtually identical cookies with gluten added. Tests and rating scales before and after the ten-day study period showed no greater improvement for those receiving the gluten-free cookies than for those receiving the gluten-added cookies. Contrary to expectations, the group receiving gluten-added cookies showed significantly greater improvement of Profile on Mood States measures of tension-anxiety and anger-hostility. Previous findings were not supported. Perhaps a longer time on the diet is required for any beneficial effects to appear.