ONCOTEST is a mid-sized company founded in 1993 by Prof. H.H. Fiebig as a spin-off of the Department of Internal Medicine of the University of Freiburg. It specializes in preclinical pharmacological contract research. With 20 years of experience in cancer research, ONCOTEST has established a unique collection of more than 200 patient-derived tumor models growing subcutaneously in nude mice. Oncotest uses only early passage tumors from cryopreserved master stocks, retaining the same histology and malignant phenotype as in the patient. Using standard-of-care drugs, the ONCOTEST tumor collection correctly predicted drug sensitivity and resistance of patients in the clinic in 92% and 97% of cases, respectively. Based on these findings, testing of experimental cancer drugs using our patient-derived tumor collection results in findings with high clinical relevance. ONCOTEST offers a wide spectrum of services including routine in vitro and in vivo screening. Test compounds are characterized in the monolayer assay by using different panels of permanent cell lines established from its patient-derived xenografts.