We explored the attitudes of women at midlife to web-based interventions for promoting physical activity. 145 women volunteered to participate in one of four online forums. The forums were for four major racial/ethnic groups. 90 volunteers were recruited for the online forums (29 Whites, 23 Hispanics, 21 African Americans, and 17 Asians). Two sets of topics on attitudes to physical activity and racial/ethnic contexts were used. Each topic had some introductory questions and related prompts, and these were posted on the online forum sites in a serial fashion during the six-month period. We used a thematic analysis. Four major themes emerged: (1) ‘a matter of the source of the information’; (2) ‘I can pace myself’; (3) ‘lack of interpersonal interactions’; and (4) ‘culture-specificity and low cost.’ The women in all ethnic groups thought that the source of the information was much more important than the medium of the information (e.g. web-based, booklet or face-to-face). They liked the self-controllability in web-based interventions. They preferred web-based interventions to other types of interventions because of easy accessibility, but they were concerned about lack of interpersonal interaction. None of the White or African American women indicated the need for culture-specificity in web-based interventions, but Hispanic and Asian women indicated that culture-specific interventions should be provided. Web-based interventions appear to have several advantages over conventional approaches to promoting physical activity.