This pilot study evaluated the safety and efficacy of intra-articular injection of hyaluronic acid (HA) in patients with hip osteoarthritis (OA). Forty-four patients affected by monolateral or bilateral hip OA were included in the study; a total of 50 joints were treated, each receiving a total of 3 to 5 intra-articular injections of 20 mg/2 ml HA. The injections were administered once each week. Evaluation of pain on movement and at rest, walking ability, and joint motion showed that RA treatment was effective in controlling pain and increasing joint mobility in 68% of the patients. The improvement observed at the end of the treatment period (30th day) was significant, compared with baseline, for pain and joint motion. This improvement continued to increase during the follow-up period up to the 60th day and was maintained up to the 180th day. Patients with mild-to-moderate disease and those receiving four injections experienced the greatest symptomatic improvement. Injections of HA were well tolerated; only one patient experienced a mild increase of pain after the first injection.