We used Ulex europaeus agglutinin I (UEAI)-immunoperoxidase staining of endothelium to study the accuracy of hematoxylin and eosin (H&E) diagnosis, occurrence, and significance of lymphvascular invasion in transitional cell carcinoma (TCC) of the bladder invading the lamina propria (Stage T1). Original histologic slides from cases (1967 to 1985) with and without vascular invasion were destained and restained with UEAI-immunoperoxidase. Only 5 of 36 biopsies originally diagnosed with lymphvascular invasion had tumor nests within endothelium-lined spaces. The 31 negative biopsies had extensive retraction artifacts lined by connective tissue and fibroblasts around tumor nests. Thirty-five control biopsies remained negative for lymphvascular invasion. Clinical follow-up of the five patients with proven lymphvascular invasion found three without progression of disease 3 to 10 yr postbiopsy, one dead of a local recurrence of TCC 1.67 yr postbiopsy, and one lost to follow-up. Based on this study, we feel that lymphvascular invasion by TCC in Stage T1 tumors is unusual, is frequently misdiagnosed on H&E stain, and does not necessarily portend a poor prognosis.