Radioimmunotherapy using (90)Y-ibritumomab tiuxetan has predominantly been used in patients with follicular lymphoma, but little is known about its activity in patients with extranodal marginal zone lymphoma of the mucosa associated lymphoid tissue (MALT). A total of six patients progressing/relapsing following conventional therapy for MALT lymphoma were treated with (90)Y-ibritumomab tiuxetan at our institution. Two patients had gastric MALT lymphoma, one suffered from orbital MALT lymphoma, and two had cutaneous MALT lymphoma, while one patient had a widely disseminated lymphoma involving the stomach, lungs, lymph nodes, and salivary glands. All patients were at least in third relapse following various forms of therapy including Helicobacter pylori-eradication, radiation, chemotherapy, and application of rituximab. Following two doses of rituximab at 250 mg/m(2) at an interval of 1 week, (90)Y-ibritumomab tiuxetan was given immediately at a dose of 0.4 mCi/kg body weight. Treatment was well tolerated apart from one episode of pneumonia requiring hospitalization. Four patients developed a complete remission (ongoing now for 4, 16, 23, and 24 months), one patient had a partial response lasting for 5 months, and one patient had stable disease for 13 months. After a follow-up of 9-29 months, all patients are alive. Application of (90)Y-ibritumomab tiuxetan is active and safe in heavily pretreated patients with MALT lymphoma.