The levels of serum selenium in 2755 individuals (1424 males, 1331 females) in Taiwan were determined by graphite furnace atomic absorption spectrometry. The average selenium concentration in serum was 110.9 microg/l with a standard deviation of 21.5 microg/l, ranging from 40.5 to 186 microg/l. The observation was higher than those recently reported in European regions but comparable to those observed in the USA or seleniferous regions. Serum selenium level did not vary with the gender, educational levels of the subjects and smoking habits. Serum selenium content seemed drop considerably if one is older than 39 years old. Age and alcohol consumption had statistically significant difference with serum selenium concentration.