Research has shown that both individual difference characteristics (e.g., sex, attachment to pets) and study-specific characteristics (e.g., type of animal used) influence the extent to which people support or oppose the use of animals in research. The current study examined how three study-specific characteristics (type of animal used, level of harm to the animal, and severity of the disease being investigated) influenced attitudes toward the use of animals in biomedical research. Participants read one of 27 scenarios describing the use of an animal in research. Scenarios systematically varied each of the study-specific characteristics described above. Participants then completed a survey to assess their support for, or opposition to, the research described. Data on attachment to pets and attitudes toward the treatment of animals were also collected. Analysis of variance revealed significant main effects for each of the study-specific characteristics. Multiple regression analyses revealed that the individual difference and study-specific characteristics accounted for 49% of the variability in opposition to the use of animals in biomedical research among men, and 37% among women. Limitations and directions for future research are discussed.