OBJECTIVES: To examine treatment patterns of ankylosing spondylitis (AS) patients who initiated anti-tumor necrosis factor (TNF) and non-TNF biologic agents, via a visualization tool. METHODS: Patients with at least one AS diagnosis were identified from the Veterans Health Administration (VHA) Medical SAS and Medicare claims datasets. Patients identified from the VHA were required to be at least 18 years old, and those from Medicare at least 65 years. AS patients who initiated therapy with anti-TNF and non-TNF biologic agents were identified. Switches from an anti-TNF to a non-TNF or vice versa within two years after initial treatment were examined. Initial treatment continuation and discontinuation rates were also calculated. Switching patterns up to two switches were identified using a processing language and illustrated in a data visualization tool. RESULTS: In the Medicare sample, 1159 AS patients initiated anti-TNF, of which 5.69% switched to another anti-TNF, 55.91% discontinued therapy and 35.72% remained on their initial therapy. A total of 532 AS Medicare patients initiated a non-TNF, of which 1.5% switched to an anti-TNF, and only 3.95% remained on the initial therapy. In the VHA sample, 1021 AS patients initiated therapy with an anti-TNF, of which 13.52% switched to another anti-TNF type, 49.56% discontinued therapy and 36.73% remained on their initial therapy. A total of 84 AS patients from the VHA initiated non-TNF therapy, of which 4.76% switched to an anti-TNF and no patients remained on their initial therapy. CONCLUSIONS: Patients who initiated anti-TNF therapy were more likely to remain with this therapy. The VHA sample had a higher switching rate than the Medicare sample. Data visualization tools can help present these complicated treatment flows effectively to researchers with a variety of specialties and backgrounds.