In December 1989, 1,457 Yami aborigines in six villages on Lanyu District (Lanyu Island), Taitung County, Southeast Taiwan, were examined by questionnaire and demonstration of the proglottides or by scotch tape perianal swab technique for taeniasis. The overall infection rate was 5%. The highest rate was found at Yehyin (8%) and the lowest at Yujen (2%). However, the rate did not significantly differ among the villages. The infection rate peaked in the 51-60 yr age group (15%) and the lowest rate was observed in the 11-20 yr age group (less than 1%). No infection was found in the 21-30 yr age group. The infection rates of men and women were similar (5%). Twenty-one per cent of 304 families was found to include one or more infected members and a family with five infected person was observed at Yehyin. The infection rate of taeniasis on Lanyu Island decreased from 16% in 1984 to 5% in 1989. However, 51 persons who were negative in 1984 were positive at present, 26 were found to be positive in both studies, and 216 (12 died) who were positive in 1984 were now negative. These results indicate that the Yami people still eat raw meat and viscera of animals.