HYPOTHESIS: Telemedicine for real-time transmission of clinical documents and interactive remote telediagnosis allows accurate clinical application in surgery. DESIGN: Prospective cohort study in which 2 hospitals, 120 miles apart, were connected via integrated services digital network (ISDN) teleconferencing units, and each evaluated clinical cases in real time. SETTING: A tertiary care university hospital and primary care county hospital. PARTICIPANTS: Between May 1, 1998, and June 30, 1998, 112 patients undergoing digestive or endocrine surgery were evaluated by teletransmission (study group) and direct vision (control group). Diagnosis had to be known by the viewer, and either conventional magnetic resonance imaging or computed tomographic scans were available. MAIN OUTCOME MEASURES: Picture quality, organ structure, and pathologic finding viewed on telemedicine documents were evaluated by radiologists and surgeons blind to diagnosis. Accuracy of remote 128-kilobit (kb)/s transmission-rate diagnoses and results were compared with those obtained directly. RESULTS: Picture quality was "good" or "excellent" in 92.9% of transmitted documents and 95.5% of live images (P>.4). The target organ was always recognized, structure and pathologic finding were analyzable in 98.2% of transmitted documents and 99.1% of live documents, and fine structures were assessable in 89.3% of transmitted pictures and 95.5% of live pictures (P>.05). Diagnosis was made in 84.8% of transmitted cases and 93.8% of live cases (P = .02). CONCLUSIONS: Low bandwidth (128 kb/s) telemedicine application in surgery is reliable in evaluating remote cases. Loss of image quality through teletransmission occurred in 2.7% of cases, and diagnosis was not possible in 15.2% of transmitted vs 6.2% of live cases, suggesting factors other than technical quality (choice of radiological studies, additional clinical information required, etc). This underscores the importance of real-time interactive discussion during surgical teleconferences.