>Evolutionary neuroandrogenic (ENA) theory asserts that brain exposed to androgens plus the brain's ability to learn accounts for most of the sex and age variations in criminal behavior. Here, the theory is extended to explain race/ethnic variations in offending. The article documents that among seven different racial/ethnic groups, blacks have the highest and East Asians have the lowest criminal involvement. Strictly social environmental explanations for race/ethnic differences in criminality appear to be inadequate for explaining these differences. Two main elements of ENA theory are offered in the present context: (a) criminal behavior is promoted by exposing the brain to testosterone and other androgens. (b) rapid postpubertal declines in offending depend heavily on learning ability. Ten lines of evidence concerning average racial/ethnic variations in androgen exposure are reviewed, and four lines of evidence of racial/ethnic differences in learning ability are reviewed. With some exceptions and qualifications, currently-available evidence seems to support the idea that racial/ethnic variations in offending could be at least partially explained by ENA theory. Closing comments are offered to suggest that biosocial approaches to the study of racial/ethnic variations in criminal behavior can help to supplement strictly social environmental theories in criminology.