Purpose: Despite the frequent occurrence of isolated calf vein thrombosis (ICVT), little is known about the long-term clinical and hemodynamic sequelae of this condition. This study was conducted to determine late clinical symptoms and vascular laboratory abnormalities in patients after ICVT. Method: Of 146 patients in whom ICVT was documented by color flow duplex scanning between 1989 and 1994, 37 were reexamined. Data included history, physical examination, venous recovery time (VRT), and duplex valve closure time (DVCT). A control group with no history of venous disease also underwent identical clinical and hemodynamic testing. Results: Thirty-seven patients (18 male and 19 female) with a median age of 56 years (range, 22 to 76 years) were examined at a mean follow-up of 3.4 years (range, 2.2 to 5.8 years) after the diagnosis of ICVT in 39 extremities. Seventeen subjects (34 extremities) were recruited as normal controls. Presenting symptoms at the time of ICVT included calf pain in 17 patients, calf swelling in seven, pain and swelling in seven, pulmonary symptoms in four, pulmonary symptoms and calf pain in one, and no symptoms in one. In the patients with ICVT, VRT was abnormal in 23% of extremities with ICVT and in 9% of extremities without ICVT. None of the extremities in the control group had an abnormal VRT (p < 0.05). DVCT was abnormal in one or more venous segments in 26% of extremities diagnosed with ICVT and in 6% of control extremities (p < 0.05). Follow-up clinical examination in patients with ICVT revealed 13 (35%) with reticular veins, 10 (27%) with varicose veins, two (5.4%) with edema, one (2.7%) with pigmentation and ulcer (contralateral extremity to ICVT with a previous history of proximal deep venous thrombosis), 13 (35%) with mild discomfort, and one (2.7%) with severe pain. All symptoms attributable to ICVT were mild in nature except in one patient who had severe pain and no physical or hemodynamic vascular laboratory abnormalities at follow-up. Conclusion: At an average of 3.4 years after ICVT, approximately one third of patients showed evidence of mild to moderate venous valvular insufficiency, but mostly in segments not involved with ICVT, and few had significant clinical symptoms attributable to venous disease.