Native American communities face major dilemmas when it comes to mainstream science. Their goals and needs could potentially benefit from contributions by science, but mainstream science has generally, historically, served nonnative cultures to the detriment of native communities. However, science may be changing for the better, relative to Native American communities and worldviews. Traditional knowledge and social-justice concerns have gained some influence with some mainstream scientists and science organizations. New advances in science and technology have created new opportunities for Native American communities to develop their economies, improve their health, and revitalize their cultures. New advances in science and technology are also, however, creating new risks and expanding some existing ones. Thus science presents Native American communities with an approach-avoidance dilemma.