A cohort of 2,131 male nitrate fertilizer workers was evaluated for cancer morbidity from 1963 to 1986. No significant increase in total cancer, stomach cancer (5 actual vs 6.7 expected cases), or lung cancer (13 vs 13 expected) was found. On the other hand, 26 actual cases of prostate cancer were observed vs 16 expected cases (standardized morbidity ratio, SMR = 161; 95%, confidence interval, CI = 107-239). This risk increase however, was, not enhanced by applying at least a 10-year latency period. In a cohort of 1,148 male fertilizer workers who had never been exposed to nitrate, there was an increased incidence of lung cancer (SMR = 151,95% CI = 103-220) but not of stomach cancer or prostate cancer. There was no association between airborne nitrate exposure dose and total cancer, stomach cancer, lung cancer or prostate cancer, respectively.