A 54-year-old male patient with heterozygous Protein C deficiency associated with the nephrotic syndrome and deep femoral artery thrombosis is described. He was admitted to the hospital because of nephrotic syndrome. A few days later, severe pain appeared in his left leg and a diagnosis of deep femoral artery thrombosis was made. Thrombectomy was performed immediately. His proteinuria disappeared in response to corticosteroid. He was found to have Protein C deficiency, antigen: 44%, activity 31%, which was also present in his father and son. Digital subtraction angiography (DSA) revealed the obstruction of left internal iliac and deep femoral arteries at their origins. Renal and hepatic biopsy revealed minor glomerular abnormalities, and chronic active hepatitis. The presence of heterozygous Protein C deficiency, nephrotic syndrome and chronic active hepatitis seem to cause marked decrease in serum Protein C level and deep femoral artery thrombosis. He is now under successful control with warfarin (1.7 mg/day) and bucolome (300 mg/day). It was reported that Protein C might have a suppressive effect on hypercoagulability in nephrotic syndrome. Therefore, Protein C deficiency may not counteract the hypercoagulable state and promote thrombus formation in the case. The present report is the first of a case of Protein C deficiency associated with nephrotic syndrome and arterial thrombosis.