Chemical, occupational, and other exposures as risk factors for non-Hodgkin's lymphoma (NHL) among homosexual men are reported from a population-based case-control study of 1593 eligible subjects with NHL and 2515 control subjects conducted in the San Francisco Bay Area between 1988 and 1995. Results are presented for 312 homosexual men with NHL and 420 homosexual control subjects. HIV-positive patients were less likely than control subjects to have worked in technical, sales, and administrative occupations; service occupations; and precision production, craft, or repair-related occupations. They were likely to have had less exposure to petroleum products, aldehydes, cleaning solvents, adhesives, insecticides, welding fumes, and tar, pitch, soot, or ash. The HIV-negative patients were less likely than the control subjects to have worked in managerial or professional specialty occupations and in technical, sales, or administrative occupations. HIV-negative patients were somewhat more likely than control subjects to have been exposed to herbicides (OR = 2.0, CI = 0.89 to 4.7), to radioactivity (OR = 4.7, CI = 1.7 to 13), and to tar, soot, pitch, or ash (250+ hours: OR = 2.3, CI = 0.96 to 5.6). HIV-negative NHL patients also were somewhat more likely to have lived on a farm as children than the control subjects (OR = 2.4, CI = 1.0 to 5.6). Pooled over HIV status, patients were somewhat more likely to have worked as motor vehicle or rail operators for more than 1 year (OR = 2.1, CI = 0.98 to 4.4). Most occupational exposures were of brief duration and many chemical exposures were reported as minimal. No clear and strong associations were found, although the risk for NHL related to exposure to several chemicals generally was reduced among HIV-positive men and elevated among HIV-negative men.