OBJECTIVES: To evaluate commonalities in presentation and long-term efficacy of treatment by percutaneous nephrostolithotomy of matrix stones, a rare form of urinary calculi. METHODS: The clinical data of 9 consecutive patients with urinary matrix calculi in 11 kidneys treated at our institution between 1995 and 2007 were retrospectively reviewed. RESULTS: The matrix component in all 11 kidneys was successfully treated with percutaneous nephrostolithotomy, with few complications. Among 8 patients (9 kidneys) with follow-up, none has had recurrence of matrix stones after a mean follow-up of 3.8 years. Along with previously known risk factors for matrix stones, such as urinary tract infections and renal insufficiency, we identified smoking as another possible risk factor. Long-term antimicrobial prophylaxis was used in only 1 patient and thus does not seem necessary for prevention of recurrence. CONCLUSIONS: Matrix stone treatment with percutaneous nephrostolithotomy is durable and should remain the treatment modality of choice.