The aim of this study was to clarify the relationship between neurologic findings and outcome of patients with West syndrome, focusing on the popliteal angle. The complete neurologic examination, including an assessment of the popliteal angle and muscle tone, was performed on 45 patients with West syndrome. A tight popliteal angle was determined when it was 120 degrees or less. In all 45 patients, abnormal muscle tone was not correlated with any variables. A tight popliteal angle was correlated with seizure persistence, cerebral palsy, and abnormality on magnetic resonance imaging (MRI), as well as severe developmental delay. When limited to the patients with developmental delay, a tight popliteal angle was correlated with severe developmental delay, cerebral palsy, and MRI abnormality, although abnormal muscle tone was not correlated with any items. In the delay group, eight patients had a tight popliteal angle with normal muscle tone. Among them, severe developmental delay was seen in seven (88%), seizure persistence in five (63%), and MRI abnormality in five (63%). These results suggest that a tight popliteal angle might be an indicator of poor neurologic outcome in patients with West syndrome.