The vascularization of cervix cancer was studied by colpophotography. Assessment of the oxygenation of the tumour surface, using the intercapillary distance as parameter, revealed a gradual decrease in the oxygenation with advancing stage of the disease. This observation was confirmed by direct measurements of the tissue oxygen tension with an open-ended polarographic microelectrode. In invasive carcinoma of the cervix, hypoxic and anoxic foci were frequently encountered. The critical intercapillary idstance seemed to be approximately 350 μ, since in cases with greater intercapillary distance the incidence of superficial necrosis rose rapidly. In 51 cases with a largest measured intercapillary distance of more than 400 μ, local recurrence was found in 51.0 per cent during 5 years of follow-up, as compared to 16.7 per cent in 54 cases with intercapillary distance below 400 μ. Out of 10 cases with a lowest observed tumour PO2 from zero to 9 mm Hg, 6 had local recurrences in the course of 4 years, as compare...