purpose: To identify clinical findings useful in estimating the probability of acute proximal deep vein thrombosis (DVT). patients and methods: The records of 355 symptomatic patients who underwent ascending venography were reviewed. Data on 76 clinical items were collected using standardized forms. Venograms were interpreted according to standard criteria and interobserver agreement was evaluated in a sample of 119 venograms. Independent clinical correlates of proximal DVT were identified using multivariate discriminant analysis in 236 randomly chosen patients; they were tested in the remaining 119 patients. conclusion: Acute proximal DVT was shown by venogram in 96 patients (27%). Five independent clinical correlates of proximal DVT-swelling above the knee of the affected leg, swelling below the knee, recent immobility, cancer, fever-predicted proximal DVT in the testing group; in patients with none, one, or two or more of these clinical findings, proximal DVT was present in 5%, 15%, and 42%, respectively. If venography had been performed only in patients with one or more of the five factors, 97% of cases of proximal DVT would have been diagnosed and venography would have been avoided in 26% of patients with normal test results. conclusion: These data provide a quantitative basis for estimating the probability of proximal DVT on the basis of clinical findings in symptomatic patients. How these findings can best be integrated with noninvasive testing and venography into diagnostic strategies for DVT remains to be determined. © 1990.