This study attempts to determine the factors which account for the fact that women are both more opposed and uncertain than men concerning the further development of nuclear energy. To that end, data from four national opinion surveys covering the period 1975-1979 are employed. Log-linear techniques are used in the analyses. Two plausible explanations for women's greater aversion to nuclear power are presented. The marginality explanation attributes the differential support of men and women for nuclear power to the differential positions which they occupy in the economic, political, and technical spheres within society. Because men hold more central positions in these areas, it is postulated that they will perceive a greater need for additional energy and continued economic growth, believe that the advantages of nuclear power toward these goals are greater, and be more confident in applications of nuclear technology. The fact that men express more favorable attitudes toward nuclear power is thus to be explained by these factors. The safety explanation attributes the sex difference to a greater concern on the part of women about the safety of using nuclear fission to generate electricity. The general thrust of this argument is that women's greater concern for safety revolves around their reproductive and nurturant roles, and the protection of future generations. Uncertainty is viewed as a special problem. An explanation for women's greater uncertainty, which attributes the difference to a sex-typed expectation concerning the formulation and expression of opinions on complex technical issues, is presented. Since children are socialized to view science and technology as primarily male fields, it is argued that the expectation to appear informed and provide opinions on technical topics like nuclear energy is less strong for women. The pattern of sex differences observed across a large number of survey items supports this view. With regard to the competing explanations for the sex difference in opposition to nuclear energy, the analyses support the safety rather than the marginality argment. Women are found to believe that nuclear power plants are less safe than men do, and to rate the problems of nuclear power as more serious. Controlling for these factors accounts for the sex difference in support for nuclear power, both in general and in respondents' local communities. Contrary to the implications of the marginality argument, women view our energy problems as more serious than men do, and there are virtually no sex differences with regard to the ratings given to various economic and other advantages of nuclear power. In line with the predictions of that argument, men are somewhat more likely to opt for producing energy over protecting the environment, and also more confident that the technical capability to rely more heavily on nuclear power currently exists. However, controlling for these factors fails to account for the sex difference. Additional topics addressed include the role of key opinion leadership groups in shaping the public opinion process concerning nuclear energy, and sex differences in reaction to the Three Mile Island accident. Women express greater confidence than men in environmentalists and Ralph Nader's organization, but no sex differences are found in confidence in scientists or the Nuclear Regulatory Commission. Hypothetical pro or con statements from each of these groups effect striking changes in the distribution of opinions of nuclear power. The magnitude of these changes in support vs. opposition is the same for both sexes. However, attaching the "expert opinion" results in a convergence of male and female uncertainty. Finally, the comparison of pre and post-TMI attitudes indicates a perception that the accident was more serious, and a greater increase in opposition to nuclear power among women.