This study aimed to identify the factors associated with the development of gastric precancerous changes, in a prospective series of patients undergoing endoscopy. Risk factors and associated mucosal changes were evaluated in 134 endoscoped patients affected by chronic non-atrophic (n= 76) or atrophic gastritis (CAG) (n= 32), with or without intestinal metaplasia (IM), or lacking any major histological changes (n= 26). The following variables were taken into account: age, alcohol consumption, smoking habit, vitamin C intake (using a questionnaire), gastric juice vitamin C (HPLC on gastric juice samples obtained at endoscopy),H. pyloriinfection, gastric mucosa malondialdehyde (MDA; a measure of free radical production) and extent of CAG in gastric biopsies (only for IM). Tissue MDA levels were significantly higher, and vitamin C levels significantly lower in CAG and IM patients (P= 0.01). Multiple regression analysis showed significant correlations for: CAGvsage (P< 0.02), MDA (< 0.02) and gastric vitamin C (< 0.05); IMvsage (P< 0.0005), CAG (< 0.0005) and MDA (< 0.001). Using stepwise discrimination analysis, the independent variables included in the model were: for CAG, age (P< 0.003), MDA (< 0.05), gastric juice vitamin C (< 0.05); for IM, CAG (P< 0.0005), age (< 0.001), MDA (< 0.03) and vitamin C intake (< 0.05).H. pyloriwas not included. The major determinants for CAG and IM were age, free radical production (as measured by MDA), vitamin C (for CAG) and vitamin C intake and CAG (for IM). Although it is instrumental in the development of gastritis,H. pyloriinfection requires major cofactors for precancerous changes to develop.