1. 311C90 is a novel and selective agonist at 5-HT1D receptors, with central and peripheral actions, currently in development for the acute oral treatment of migraine. 2. The pharmacokinetic and tolerability profiles of single oral doses from 1-50 mg 311C90 were investigated in 12 healthy male volunteers in a double-blind, placebo-controlled, dose-escalating study. 3. 311C90 was well tolerated with most adverse experiences of mild and transient nature. 4. Absorption was rapid with dose-independent kinetics. Median tmax was 2-4 h although 50-85% of eventual Cmax was attained within 1 h. The t1/2 was 2.5-3 h with a high apparent plasma clearance (CL/F > 2000 ml min-1) and apparent volume of distribution (Vz/F) of 400-500 l. 5. Three metabolites were detected in plasma and urine, one of which, the N-desmethyl metabolite, has 5-HT1D agonist activity. 6. 311C90 showed no clinically significant effects on blood pressure, heart rate, ECG or laboratory variables at any dose and demonstrated a tolerability and pharmacokinetic profile compatible with an acute oral migraine treatment.