OBJECTIVE:To compare the efficiency and differential costs of telephone- vs. mail-based assessments of outcome in patients registered in a national clinical quality of care registry, the Australian Stroke Clinical Registry (AuSCR). STUDY DESIGN AND SETTING:The participants admitted to hospital with stroke or transient ischemic attack were randomly assigned to complete a health questionnaire by mail or telephone interview at 3-6 months postevent. Response rate, researcher burden, and costs of each method were compared. RESULTS:Compared with the participants in the mail questionnaire arm (n=277; 50% female; mean age: 70 years), those in the telephone arm (n=282; 45% female; mean age: 68 years) required a shorter time to complete the follow-up (mean difference: 24.2 days; 95% confidence interval [CI]: 15.0, 33.5 days). However, the average cost of completing a telephone follow-up was greater (US$20.87 vs. US$13.86) and had a similar overall response to the mail method (absolute difference: 0.57%; 95% CI: -4.8%, 6%). CONCLUSION:Posthospital stroke outcome data were slower to collect by mail, but the method achieved a similar completion rate and was significantly cheaper to conduct than follow-up telephone interview. Findings are informative for planning outcome data collection in large numbers of patients with acute stroke.