Forty-four randomized, partially gastrectomized subjects were studied to assess whether gastric histologic findings after partial gastrectomy were related to reflux. Gastric biopsy specimens (12) were taken at different distances from the anastomosis. Histologic findings were as follows: (a) hyperplastic changes of the foveolar epithelium and (b) loss of the chief and parietal gland cells with atrophy of gastric glands (chronic atrophic gastritis). Hyperplastic changes typical of the perianastomotic area gradually decreased with increasing distance from the anastomosis. Hyperplastic changes showed a greater prevalence in Billroth II than in Billroth I subjects (100% vs. 29.4%). No significant association was found between histologic findings and symptoms. Hourly bile acid quantity (fasting bile reflux) and concentration were determined in the gastric aspirates. Bile reflux was greater after Billroth II than after Billroth I (fasting bile reflux median values: 30.5 vs. 0.18 mumol/h, respectively). The same was true for bile acid concentration (mean bile acid concentration median values: 624.9 vs. 17.5 mumol/L, respectively). Moreover, Billroth I subjects with hyperplasia had a greater quantity and concentration of reflux than those without hyperplasia (fasting bile reflux and mean bile acid concentration median values: 2.6 vs. 0.8 mumol/h and 4.7 vs. 2.7 mumol/L, respectively). These findings show that bile reflux is correlated with hyperplastic changes of the foveolar epithelium, but prevalence and severity of atrophic gastritis were not related to reflux. Therefore, although we failed to show any relationship between chronic atrophic gastritis and reflux, foveolar hyperplasia was shown to be reflux related.