BACKGROUND: Our aim was to set reference intervals of healthy adults using Beckman Coulter LH 750 by gender and age. METHODS: The specimens were obtained from a total of 705 healthy adults (male 484, female 221), who took part in annual health-check at Chungnam National University Hospital, analyzed in total 22 parameters and compared using SPSS V10.0 program. RESULTS: Totally 16 parameters showed the Gaussian distribution with 12 in parametric method and 4 in logarithmically transformed parametric method. All acquired reference intervals were showed in Table 3, 4, 5 and 6. There were statistical significances between genders in RBC, Hgb, Hct, MCV, MCH, WBC, EO%, LY#, MO#, EO#, MPV, PDW (P<0.001), BA% (P=0.001), NE% (P=0.016), BA# (P=0.019), MO% (P=0.021) and NE# (P=0.039), between age decades in RBC, Hgb, Hct, MCV, MCH, NE%, LY% (P<0.001), LY# (P=0.002), EO%, NE# (P=0.003) and Pct (P=0.033) as well as between genders and age decades in RBC, Hct (P=0.001), Hgb (P=0.004), LY# (P=0.005), Plt (P=0.014) and MO% (P=0.017). CONCLUSIONS: This study suggested that the reference intervals of RBC and Hgb ought to be set by both genders and age decades, WBC by gender and the others by total study populations. Moreover, it need to be set the reference intervals by each laboratory for itself and to be monitored with periodic review.