Effects of dose titrationMultiple sclerosis (MS) treatment with interferon beta is associated with well-known, easily managed adverse events, including influenza-like symptoms and injection-site reactions that decline over time. Initial dose titration has been shown to be one way of limiting these adverse events. Hence, a placebo-controlled, multicentre study of 98 patients was set up to explore whether a slower, four-stage, 4-week titration to a final dose of 250 microg subcutaneous interferon beta-1b might improve tolerability over a more rapid two-stage, 2-week titration in patients with relapsing-remitting MS. Frequency of adverse events was found to be similar between the two regimens: notably, no difference in the incidence of injection-site reactions, with a trend towards fewer influenza-like symptoms in the slow-titration group. Relative to placebo, significantly fewer patients receiving interferon beta-1b relapsed. This was more pronounced in the rapid-titration group than in the slow-titration group, showing that rapid and significant improvements in relapse rates were achieved within 90 days of starting interferon beta-1b. Although a rapid-titration regimen results in a quicker onset of clinical benefit, slow titration showed a non-significant trend towards reduced influenza-like symptoms.