This paper is the continuation of previously published work, a review limited to studies on rats and mice. This paper makes an identical evaluation as before, but, restricting the species being evaluated to representative studies of smoke-exposed hamsters, dogs (both by tracheostomy and by direct inhalation), and nonhuman primates. As was seen previously, no statistically significant increase in the incidence of malignant tumors of the respiratory tract was found in any of the 3 species, even though very long exposures and high doses of smoke were used. All 5 of the species of laboratory animals commonly used to evaluate carcinogenic potential produce results with mainstream cigarette smoke that are at variance with the epidemiological evidence in smokers.