Fifteen cases of inflammatory fibroid polyps (IFPs) of the gastrointestinal tract were subjected to histopathologic analysis. Six of them were from the small intestines and the remainder from the stomach. Their size ranged from 0.2 to 12.0 cm in maximum cross-section. The polyps were classified into four groups, based on histology and size. The nodular stage (average: 0.4 cm) showed nodules of immature fibroblasts with a loose myxoid background resembling a tactile corpuscle of Meissner. The fibrovascular stage (average: 1.5 cm) demonstrated concentric aggregations of mature fibroblasts, with endothelial proliferation and eosinophilic infiltration. When the polyps became larger (average: 4.8 cm), the histologic patterns were modified, evolving into the sclerotic or edematous stage by either collagenization or vascular compromise following intestinal obstruction. This study suggests that histologic patterns of IFPs may represent an evolutional change when size is increased.