A single-dose, double-blind, randomized clinical trial was conducted to examine the relative analgesic effectiveness of 400 mg of ibuprofen (n = 153), 1,000 mg of acetaminophen (n = 151), and placebo (n = 151) in volunteers with muscle contraction headache. At regular intervals during a 4-hour period, participants evaluated headache pain intensity on a 100-mm visual analog scale and headache pain relief on a six-category scale. Both active agents were significantly different from placebo at all time points and in reducing pain intensity and providing relief of headache overall. Similarly, ibuprofen at 400 mg differed significantly from acetaminophen at 1,000 mg on both rating scales. Participants receiving ibuprofen at 400 mg achieved complete relief of headache faster than those receiving acetaminophen at 1,000 mg or placebo, and more participants taking ibuprofen experienced complete relief of headache than those taking placebo or acetaminophen. Both ibuprofen at 400 mg and acetaminophen at 1,000 mg are efficacious analgesic agents for muscle contraction headache, and ibuprofen at 400 mg is significantly more effective than acetaminophen at 1,000 mg for treating this condition.