Patients with rare illnesses may use medication information sources that are appreciably different from those used by patients with more common illnesses. This article's purpose is to describe vasculitis patients' most frequently used medication information sources, determine which sources patients perceive as credible, and explore gender differences in source use and perceived credibility. Using an online questionnaire, patients (n = 232) indicated how often they obtained medication information from 12 sources during the previous year and rated the credibility of 6 sources. The authors used multivariate analysis of covariance and follow-up contrasts to test for gender differences in source use and conducted t tests to compare patients' perceived credibility ratings. Patients used physicians and the Internet most often to obtain medication information and rated them as the most credible sources. Male patients used their spouse/partner more often and rated them as more credible than did female patients. Female patients were more likely to use medication package inserts and the Internet and were less likely to use nurses than were male patients. There appear to be similarities and differences between the information-seeking behaviors of vasculitis patients and other patient populations. Because male patients view their spouse/partner as a credible information source, providers may want to involve the spouse/partner in prescription decision making.