Throughout most of the 20th century in the United States, biological arguments that link biochemistry, genetics, neurophysiology, or some combination have been unthinkable and unmentionable. However, the results of this analysis revealed that the taboo surrounding biocriminology appears to be diminishing in textbooks. Newer texts devoted more coverage to biological perspectives than did older textbooks. They were also more likely to claim that at least some empirical evidence supports these arguments. In addition, criminology textbooks based on interdisciplinary orientations were less likely to depict biological arguments as taboo than were those that endorsed sociological orientations, especially critical sociological orientations. Tables, notes, list of textbooks examined, and 118 references (Author abstract modified)