Theophylline, a drug used by 6-10 million patients, needs to be monitored closely in blood for effective management of asthmatic, allergic, and other bronchospastic conditions. Current tests for theophylline are based on expensive antigen-antibody technologies. Health insurance reimbursements for such measurements is between $27.00 and $37.00 per test. Alternatively, GDS Technology has discovered a unique enzyme, Theophylline oxidase, which selectively oxidizes theophylline in the presence of various electron acceptors (patents pending). Phase I research has clearly established that Theophylline oxidase is suitable for use in a stable liquid phase reagent test for measuring theophylline in serum (already an FDA approved test) and has potential for use in a new dry strip-test format. Phase II research will involve l) incorporation of an appropriate electron acceptor dye (found in Phase I study) along with Theophylline oxidase in a dry strip-test configuration, 2) development of a low cost reflectance meter, 3) pilot scale production of the strip-test, and 4) preliminary clinical evaluation of the new test. It is anticipated that this research could yield a suitable method for """"""""on-site"""""""" testing of theophylline in whole blood. The test will yield accurate results and will sell for less than $2.00/test, thus providing quality health care at a significantly reduced cost.