Non-Hodgkin's lymphomas of the orbit and ocular adnexa (OOA), the majority of which are extranodal marginal zone B-cell lymphomas of mucosa-associated lymphoid tissue-type (MALT lymphomas), are a rare disorder. The aim of this study was to evaluate the clinical features and treatment outcomes and complications in patients with MALT lymphoma of OOA. Thirty-seven patients with a histologically verified diagnosis of MALT lymphoma of OOA were included in this retrospective, observational case study. There were 22 (59%) men and 15 (41%) women, with a median age of 44 years (range, 21-80 years). The most common presenting complaint was a slowly growing orbital mass. The stages were IA(E) in 74%, IA(EE) (bilateral involvement) in 18%, IIIA(E) in 6%, and IVA(E) in 3%. None of the patients had an elevated value of LHD or beta(2)-microglobulin. Surgical resection alone was attempted as the sole treatment in two patients, but tumor recurred 19 and 24 months after surgery. Radiotherapy, with a median tumor dose of 3,060 cGy, was administered in 29 patients; all of the patients achieved complete remission, and none of them had severe later complications. Combination chemotherapy alone was employed in three patients with stage IIIA(E) or IVA(E). With a median follow-up duration of 21 months, the 3-year overall survival (OS) rate and event-free survival (EFS) rate were 97% and 86%, respectively. Subgroup analysis of the patients with localized disease, who received radiotherapy as an initial treatment modality, revealed that 3-year OS rate and EFS rate were 100% and 93%, respectively. All disease recurrences were documented histologically as MALT lymphoma. In conclusion complete staging evaluation is needed to select an adequate treatment modality. Radiotherapy alone can produce excellent local control and survival in patients with localized MALT lymphoma of OOA. Systemic chemotherapy should be considered in patients with advanced stages or systemic manifestation.