Thirty to forty percent of migraineurs do not respond to any given triptan treatment. We identified clinical variables that significantly predict therapeutic non-response and evaluated the efficacy of eletriptan (20, 40 and 80 mg) and sumatriptan (100 mg) vs. placebo in a subgroup of patients with all predictor variables. First-attack data were pooled from 10 randomized, double-blind, placebo-controlled migraine trials (n = 8473). Multivariate regression analyses identified three significant baseline predictors of failure to achieve 2-h pain-free response: severe headache pain, presence of photophobia/phonophobia and presence of nausea. Time of dosing following headache onset did not influence 2-h pain-free response. Among patients with all three risk factors (n = 2010; 24% of total sample), 2-h pain-free response was significantly higher in patients receiving all three doses of eletriptan or sumatriptan vs. placebo (all P < 0.01). Thus, eletriptan and sumatriptan are efficacious in difficult-to-treat patients at high risk for non-response to triptans.