We evaluated the types, frequency, and significance of stromal reaction patterns in urothelial carcinoma (UC) of the bladder in 60 transurethrally resected pT1 specimens (low-grade UC, 12; high-grade UC, 48). We observed 5 reaction patterns with 1 pattern in 37 cases (62%) and 2 or more patterns in the remainder. Dominant and secondary patterns, respectively, were as follows: stromal retraction, 30 (50%) and 4 (7%); edema, 18 (30%) and 1 (2%); inflammation, 8 (13%) and 14 (23%); fibroblastic proliferation, 3 (5%) and 5 (8%); fibrosis, 1 (2%) and 4 (7%). Progression occurred in 21 cases, including 9 (30%) of 30 with stromal retraction, 8 (45%) of 18 with edema, 2 (25%) of 8 with inflammation, 1 (33%) of 3 with fibroblastic proliferation, and 1 (100%) of 1 with fibrosis. Differences in progression rates and mean progression-free survival times were not statistically significant. We found that the most common stromal reaction in UC of the bladder is stromal retraction. Stromal reaction patterns seem to have some prognostic usefulness. Cases with stromal edema might benefit from closer follow-up. Awareness of the different types of stromal reactions also is useful for diagnosing invasion.