The nematocide 1,2-dibromo-3-chloropropane (DBCP), widely used in Costa Rica during the late 1960s and 1970s, causes sterility in men and is a possible carcinogen. Mortality among a cohort of Costa Rican banana plantation workers was investigated. The cohort included 40,959 individuals who worked on banana plantations between 1972 and 1979. Employment records were linked with the Costa Rican Mortality Registry to determine outcomes through 1999. Standardized mortality ratios (SMRs) were calculated for all causes of death. Poisson regression was also used to calculate mortality risk estimates by duration of employment, but provided no additional insight. All-causes SMRs were 0.77 for men (95% CI 0.75-0.80) and 0.90 for women (95% CI 0.80-1.02) relative to national mortality rates. Mortality from septicemia was significantly higher than expected. Nonsignificant increases in mortality were also observed for testicular cancer, penile cancer, Hodgkin's disease, and Parkinson's disease in men, and for cervical cancer and lung cancer in women.