A double-blind, 18-center, balanced trial of diflunisal vs. cyclobenzaprine HCl vs. these two drugs combined vs. placebo produced complete results from 175 patients. They had sought treatment at the cooperating centers for acute painful spasms of the back within a day or two of trauma or strain. Global results over the 7 to 10 days of observations revealed a clinically and statistically significant superiority of the combined therapy by Day 4 (P = 0.006) and almost all patients recovered within a week to 10 days. A combination therapy with an effective safe analgesic and a true muscle relaxant for less than a week appears to be an excellent relief measure for acute back problems.