Hypoxia-inducible factor 1 (HIF-1) plays an important role in human cancer cell invasion and metastasis. As a result, overexpression of the HIF-1alpha subunit in biopsy specimens is associated with increased patient mortality in several common cancers, including breast adenocarcinoma and oropharyngeal squamous cell carcinoma. Here, we describe methods for immunohistochemical detection of HIF-1alpha in tumor biopsy sections and ex vivo assays for analyzing the effects of hypoxia and HIF-1 on cancer cell invasiveness and cell-cell adhesion.