After total hip arthroplasty, long-term complications such as loosening, wear, osteolytic lesion and granulomatous reaction by foreign bodies can occur. Granulomatous reaction is a chronic inflammatory reaction caused by polyethylene debris, which is rarely present as a mass. The case of a pseudotumor, which required surgical intervention because of pain and its large size with compression symptoms, has not been reported yet. This 70 year old male patient was admitted complaining of RLQ pain, a palpable mass and compressed adjacent organs, 2 years after a revision total hip arthroplasty performed in September 1999. During the operation, a well-encapsulated large mass was noted, which was near the lateral side of the iliopsoas muscle and compressed the femoral nerve from the posterolateral side. Here, we report a case of pseudotumor caused by polyethylene wear debris.