Deep-vein thrombosis of the lower extremity is a frequent disorder associated with morbidity and mortality due to pulmonary embolism and the postthrombotic syndrome. It was not until the introduction of contrast venography that the inaccuracy of the clinical diagnosis became apparent. Since then, management decisions have usually been based on objective diagnostic test. Venography is generally considered the reference method for the diagnosis of deep-vein thrombosis, but it is invasive and associated with serious side effects. Several noninvasive or less invasive objective diagnostic methods have been developed. These diagnostic methods are distinctly different in technology and consequently in their ability to demonstrate or refute deep-vein thrombosis. In this review, a critical analysis is provided on the accurary of the current noninvasive diagnostic approaches to venous thrombosis in patients with a first episode of clinically suspected deep-vein thrombosis. Results of studies were considered only when their methodology fulfilled the essential criteria for evaluation of a diagnostic test.