['In patients with suspected pulmonary embolism (PE), an unlikely or non-high probability assessment combined with a normal D-dimer test can safely exclude the diagnosis. We studied the influence of early D-dimer knowledge on clinical probability assessment.', 'A questionnaire was sent to 150 randomly selected pulmonologists and internists in the Netherlands, presenting six hypothetical case-descriptions of patients with suspected PE. Physicians were randomized to receive one of three versions. The version contained a normal, an abnormal or no D-dimer result with each case-description. Each version contained two cases with an abnormal D-dimer result, two cases with a normal D-dimer result and two cases with no D-dimer result.', 'A total of 71 physicians (47%) returned the questionnaire; the three versions were equally represented. Compared to the control cases in which no D-dimer was given, knowledge of an abnormal D-dimer resulted in more "likely" clinical scores using the Wells\' score (absolute increase in "likely" of 25-37%, p=0.005, 0.111 and 0.144), while knowledge of a normal D-dimer resulted in more "unlikely" scores (absolute increase in "unlikely" of 27-44%, p=0.001 and 0.070). D-dimer knowledge did not influence the probability assessment when the clinical suspicion was very high.'] Do knowledge of the D-dimer test result influences clinical probability assessment of pulmonary embolism?