Standardized incidence ratios (SIR) of malignant neoplasms in Taiwanese Aborigines were analyzed. In all, 995 cases of cancers had been reported in 30 Taiwanese Aboriginal communities between 1981 and 1987. In the same time period, 137, 159 cases were registered in Taiwan and carefully categorized according to race, gender, site and frequency of occurrence. Sex and tribe-specific standardized incidence ratios with 95% confidence interval were calculated. We found that the standardized incidence ratios of all cancers in Aborigines was lower than that in the general population of Taiwan for both Aboriginal men (0.72, 95% CI:0.67-0.78) and women (0.66, 95% CI:0.59-0.72). Of selected malignant neoplasms, SIR for nasopharyngeal carcinoma was slightly elevated in men, especially in the Bunun and Rukai tribes and significantly elevated in Paiwan women (2.95, 95% CI:1.65-4.87). The SIR for gastric cancer was significantly elevated for both men (SIR = 1.22, 95% CI:1.03-1.44) and women (1.48, 95% CI:1.14-1.92), especially in Atayal and Bunun men and Atayal women. There was a higher than expected level of incidence of penis cancer and other male genital cancers, especially in Paiwan people, with the SIR as large as 6.24 (95% CI:2.02-14.53). The SIR of lymph node cancer was significantly increased in Bunun (4.21, 95% CI:1.36-9.81) and Yamei women (CI:1.50-44.89), but not for all Aboriginal men. Colon, rectum, lung, bladder and oral cancers in aboriginal men and colon, rectum, lung, breast and cervical cancer in women occurred significantly less frequently than in the general population. The SIR of colon and rectum carcinoma was significant lower for both men (0.45, 95% CI:0.32-0.61) and women (0.25, 95% CI:0.13-0.42), particularly in the Atayal and Paiwan tribes. The SIR of lung cancer was 0.52 (95% CI:0.41-0.66) in Atayal, Bunun, Paiwan men and 0.58 (95% CI:0.38-0.86) in Paiwan women. There were significantly lower than expected levels of incidence of bladder (0.18, 95% CI:0.02-0.65) and oral cancer (0.29, 95% CI:0.08-0.74) for Atayal men. Aboriginal women had significantly lower SIR of cervical cancer (0.46) especially in Atayal, Bunun, Paiwan women and of breast cancer (0.38) especially in the Atayal and Paiwan women. But cancer of esophagus, liver, gallbladder, pancreas, and prostate occurred among Aboriginal people at the same rate as in the general Taiwan.