In forensics and archaeology, it is important to distinguish human from animal remains and to identify animal species from fragmentary bones and bloodstains. We report blind tests in which a protein radioimmunoassay (pRIA) was used to identify the species of six bone fragments lacking morphological specificity and 43 bloodstained lithic tools, knapped experimentally and soaked in blood of known animal and human origin. The submitters of the bone fragments and the bloodstained tools each listed a number of possible species, from which the testers selected the best match with the pRIA results. All six bone fragments were correctly identified: three humans, a deer, a dog, and a cow. Forty-three tools were stained with blood from a wide variety of species including ungulates, carnivores, a fish, and a bird. On 40 of these 43, at least one species (or blood-free control) was identified correctly. Some of the tools were stained with blood of two different species. A mixture of sheep and musk ox blood was correctly identified; in several other mixtures, only a single species was detected. Two tools with human blood and one with human sweat were correctly reported as human. There was a single false positive (one of three controls reported as weakly bovine) and no false negatives. We conclude that the pRIA technique shows a high degree of accuracy in discriminating human from animal bone fragments and bloodstains and in identifying animal species.