Introduction Niacin is underutilised because of flushing. Lack of a quantitative tool to assess niacin-induced flushing has precluded the objective evaluation of flushing associated with extended-release (ER) niacin formulations. We developed the Flushing Symptom Questionnaire© (FSQ), a quantitative tool to assess patient-reported flushing, and assessed its ability to characterise ER niacin-induced flushing. Methods This study focused on the responses to one question in the FSQ, the Global Flushing Severity Score (GFSS), reported on a 0–10 scale (none = 0, mild = 1–3, moderate = 4–6, severe = 7–9 and extreme = 10) to assess flushing during ER niacin initiation (week 1) and maintenance (weeks 2–8). Results Flushing severity with ER niacin was greatest during week 1 and remained greater than placebo for the study duration. During weeks 2–8, 40% of patients on ER niacin vs. 8% of those on placebo had > 1 day/week with ‘moderate or greater’ GFSS. Conclusions In conclusion, the GFSS component of the FSQ was a sensitive and responsive quantitative measure of ER niacin-induced flushing that will aid in the objective comparison of novel strategies intended to improve tolerability and adherence to niacin, an agent proven to reduce cardiovascular risk. Disclosures John F. Paolini, Yale B. Mitchel, Robert Reyes, Sally Thompson-Bell, Qinfen Yu, Eseng Lai, Douglas J. Watson, Josephine M. Norquist and Christine McCrary Sisk are employees of Merck & Co., Inc., and may own stock/hold stock options in the Company. Dr Harold Bays has served as a Clinical Investigator for (and has received research grants from) the following: Abbott, Alteon, Arena, AstraZeneca, Aventis, Bayer, Boehringer Ingelheim, Boehringer Mannheim, Bristol Myers Squibb, Ciba Geigy, Eli Lilly, Esperion, Fujisawa, GelTex, Genentech, GlaxoSmithKline, Hoechst Roussel, Hoffman LaRoche, InterMune, KOS, Kowa, Lederle, Marion Merrell Dow, Merck, Merck Schering Plough, Miles, Novartis, Parke Davis, Pfizer, Pliva, Purdue, Reliant, Roche, Rorer, Regeneron, Sandoz, Sankyo, Sanofi, Searle, Shionogi, Schering Plough, SmithKline Beacham, Takeda, TAP, UpJohn, Upsher Smith, Warner Lambert and Wyeth-Ayerst. He has also served as a consultant, speaker, and/or advisor to and for Arena, AstraZeneca, Aventis, Bayer, Bristol Myers Squibb, KOS, Merck, Merck Schering Plough, Metabasis Therapeutics, Microbia, Novartis, Nicox, Ortho-McNeil, Parke Davis, Pfizer, Roche, Sandoz, Sankyo, Sanofi Aventis, Shering Plough, SmithKline Beacham, Takeda, UpJohn and Warner Lambert. What's known Niacin has favourable effects on the lipid profile; however, its use in clinical practice has been hampered by bothersome side effects, primarily flushing. The lack of a quantitative tool to assess flushing symptoms has precluded the objective evaluation of niacin-induced flushing. What's new This study describes the utility of the Flushing Symptom Questionnaire© (FSQ), a quantitative tool to assess patient-reported flushing end-points. The results show that the FSQ is a useful patient-reported outcome measure to objectively assess flushing associated with extended-release niacin.