Test strips recently have become available to measure theophylline levels. One such test strip (AccuLevel) had not been tested in an actual clinical situation with nontechnician personnel. We prospectively evaluated the test strip on consecutive emergency department patients, comparing it with the agglutination inhibition method used by our hospital laboratory. Nurses and medics who ran the test were given only a brief demonstration and explanation of the manufacturer's instructions. The 61 test strip levels correlated highly with the laboratory results (r = 0.92, slope = 0.89, y-intercept = 0.99). The test strip results were available in less time (mean of 0.51 hours vs 1.89 hours for the laboratory, P less than .0001). The most accurate readings were obtained by those who ran the test most frequently. Caffeine intake did not influence the test. Cost was significantly lower than charges at local hospitals.