Studies from different countries showed variations of genetic changes and association with Chlamydia psittaci in ocular adnexal mucosa-associated lymphoid tissue (MALT) lymphoma. A total of 38 ocular adnexal MALT lymphoma cases from Northern China were studied. Genetic abnormalities were investigated in 28 cases by interphase FISH. C. psittaci and other infectious agents that are commonly-associated with chronic eye disease were screened in 38 cases by PCR. Genetic abnormalities were detected in 60.7% of cases. Among them, only one showed a break-apart of the IgH gene and all others showed numerical abnormalities, including trisomy 18 in 7 cases (25%), 3 copies of BCL6 gene in 12 cases (43%), and 3 copies of C-MYC gene in 2 cases (7%). C. pneumoniae was positive in two cases (5.3%), and C. psittaci, C. trachomatis, HSV1, HSV2, ADV8, and ADV19 were not detected in any cases. In conclusion, numerical abnormalities are frequent and the chromosomal translocations commonly associated with MALT lymphomas are rare in ocular adnexal MALT lymphoma of Northern China. C. psittaci and other infectious agents are not associated with ocular adnexal MALT lymphoma in these patients.