Comparative Biosciences, Inc. (CBI), a preclinical contract research organization (CRO), provides expertise in investigative, custom, and special toxicology services. There is often a need for specialized and complex toxicology studies, generally to address unanticipated or unusual toxicologic events or to conduct toxicology studies that are of a difficult or unusual nature. These investigative, custom, and special toxicology studies are directed, hypothesis-driven, and may have specialized or unusual techniques or methods. In some cases, they are requested by the FDA or by clinicians. Examples might include CT or PET scanning, specialized immunohistochemistry, surgical aspects, application of test article surgically, or esoteric blood samples. The skilled scientists at CBI can facilitate the protocol development as well as the conduct of these difficult and specialized projects.