Despite advances in the treatment of asthma the morbidity and mortality of this disease has increased significantly in the past several years. Recent studies have shown that monitoring of asthma severity in the patient home especially combined with patient education can reduce incidence of asthma exacerbation and subsequent hospitalization. The existing methods for home asthma monitoring are limited by four factors; they completely rely on a patient's ability to document and to evaluate test results; there is no easy way for a physician to review data in a timely manner; they use imprecise tools for evaluation of asthma severity and they don't provide clinical decision support tools. The goal of this study is to develop and to evaluate a telematic system for asthma severity monitoring which will minimize patients' efforts in performing self-testing at their homes and allow prompt reciprocal exchange of all relevant information between patients and health care providers. In our setting, patients use portable spirometer and pocketsized palmtop computer for data exchange. Our system allows daily serial monitoring of asthma severity at patients' homes using Forced Vital Capacity test and symptom diary. The results of the tests become available for physicians review immediately after completion of self-testing procedures via Web browser. The results can be transmitted from patients' homes (or any other remote location) to the medical records database via landline or wireless networks in several minutes. Each time the remote server receives patient's results, it invokes the application which tests the validity of data, analyzes parameters trends and dispatches corresponding messages for the patient and, if necessary, for physicians. Such an approach provides constant feedback loop between asthma patient and physician. The system has been tested in 10 healthy volunteers and asthma patients. Patients participated in the study from two to 21 days. The test results showed that the system provides reliable reciprocal exchange of all relevant information between a physician and asthma patient in home settings. Average transmission time from the patient's palmtop to the remote central data repository was about 1 minute for 14.4 Kbps landline modem, 6 minutes for cellular network and 8 minutes for RAM Mobile network. After transmission, the test results were immediately available for review at our web site.