A recent report suggesting that ocular adnexal non-Hodgkin lymphoma (NHL) may be related to Chlamydia psittaci infection underscores the need for reliable epidemiologic data for this malignancy. We examined population-based incidence data from the Surveillance, Epidemiology, and End Results (SEER) Program. During 1992-2001 in the 12 SEER areas, ocular (i.e., eye and adnexa) NHL rates per 100,000 person-years for both sexes were highest among Asians/Pacific Islanders, lower in whites, and lower still in blacks. Incidence increased with advancing age and showed little difference by sex, in contrast to other (extranodal and nodal) NHLs, which occurred predominantly in males. From 1975-2001, there was a rapid and steady increase in incidence of ocular NHL, with annual increases of 6.2% and 6.5% among white males and females, respectively, with no evidence of peaking. By contrast, other NHLs showed evidence of peaking in recent years. The distinctive patterns of ocular NHL call for further studies to identify risk factors and mechanisms, including the potential role of C. psittaci or other infections.