This laboratory has recently reported the solubility and in vivo absorption enhancement of diclofenac sodium by ${eta}-cyclodextrin$ complexation. The acute gastroduodenal mucosa injury provoked by administration of 34 mg/kg and 68 mg/kg of a diclofenac sodium (DS) and equivalent dose of new formulation [diclofenac sodium-beta-cyclodextrin complexation$(DS-{eta}-CD)$] was evaluated and compared. Microscopic examinations, performed after 18-hrs treatment, demonstrated that $DS-{eta}-CD$ was less gastrolesive than DS. The drop in gastrophy after a single dose of the assigned drug was considerably greater for DS than for $DS-{eta}-CD$, which registered similar values to control. Since gastrophy is an expression of the anatomy-functional integrity of the gastric barrier, the results indicate that $DS-{eta}-CD$ exerts less direct acute damage on the gastric mucosa. Therefore, when administered short-term, $DS-{eta}-CD$ appears to be less gastrolesive than the standard DS formulation.