Samples of serum, liver, kidney, and heart were collected for selenium analysis from 174 white-tailed deer (Odocoileus virginianus) in southern Florida (USA), 1984 to 1988, to determine the selenium status of these animals. Deer were obtained from eight sites and classified by five age-class groups. For serum and the three tissues analyzed, selenium concentrations varied significantly (P < 0.001) among sites. Differences between years (P < 0.0004) were found for heart and kidney, age-class (P < 0.004) for kidney and season (P < 0.02) for liver. Low selenium concentrations were evident, in that 75% of all serum samples analyzed contained less than the critical concentration (< 0.06 ppm) by livestock standards, with 50% of serum samples less than 0.03 ppm, evidence of a severe deficiency. Likewise, tissue selenium concentrations (dry basis) were below critical livestock concentrations in 13% of the liver samples (< 0.25 ppm), 36% in kidney (< 3.0 ppm) and 19% in heart (< 0.15 ppm). Based on serum and tissue data, selenium dietary intake was low and may have been deficient for white-tailed deer in southern Florida.