This is a double-blind, randomized, vehicle-controlled, parallel-group, multi-center, phase III efficacy and safety study of civamide nasal solution 0.01% in the prevention of cluster headaches during an episodic cluster headache period. Approximately 180 subjects (about 90 per treatment group),will be enrolled and randomized to double-blind treatment with either civamide nasal solution 0.01% or vehicle solution at approximately 50 study sites with about 2-5 subjects randomized per enrolling site.