Dark field microscopy, also called live blood analysis, according to Enderlin claims to be able to detect forthcoming or early cancer through minute abnormalities in the blood. In Germany and the USA this method is used by an increasing number of physicians and health practitioners. Blood samples were drawn for dark field microscopy in 110 patients. A health practitioner with several years of training in the field carried out the examinations without prior information about the patients. Out of 12 patients with present tumour metastasis three were correctly identified. Analysis of sensitivity (0.25), specificity (0.64), positive (0.09) and negative (0.85) predictive values revealed unsatisfactory results.