This study developed and tested the Toronto Informational Needs Questionnaire-Breast Cancer (TINQ-BC), a questionnaire designed to identify the information which women with a recent diagnosis of breast cancer need to deal with their illness. The 73-item questionnaire had content validity based on findings in the literature and opinions of expert oncology nurses. It was administered to 114 women with a recent diagnosis of breast cancer during chemotherapy (n=39), radiation therapy (n=40) or surgery (n=35). Item analysis determined that 51 items in five subscales should be retained in the questionnaire. The subscales, labeled Disease, Investigative Tests, Treatments, Physical, and Psychosocial had good internal consistency reliabilities with Cronbach's alphas of 0.81 to 0.93. Informational needs of women were high with mean scores over 200 in a possible range of 51-255. Informational needs were greatest in either the Disease or Treatments subscales. Marital status, level of education, and level of income were not related to level of informational need. Younger women had a greater need for information than older women (r=-0.35, P=0.003). The results suggest that information is important to help women with breast cancer manage their illness. Nurses should give women an opportunity to ask questions and be prepared to give accurate information.