A comparison of serum electrolytes between commercial and self-prepared reagents was performed using a Beckman CX-3 delta automatic analyzer. The precision was evaluated by analyzing three levels of control sera. The within-run coefficients of variation (%CV) of sodium, potassium, chloride and carbon dioxide for commercial reagents were 0.35-0.42%, 0.29-0.52%, 0.37-0.64% and 1.54-3.28% respectively and the between-run coefficients of variation (%CV) of the method ranged from 0.29-0.54%, 0.42-0.58%, 0.60-0.82% and 3.66-4.40% respectively, whereas those of the selfprepared reagents were 0.26-0.37%, 0.39-0.55%, 0.48-0.69% and 1.54-4.16% respectively, and between-run 0.32- 0.55%, 0.41-0.81%, 0.63-0.93% and 4.31-5.03% respectively. There was also good correlation (r) of serum electrolytes measurement in 100 patients at (0.981, y=0.996x+0.356), (0.995, y=1.042x-0.228), (0.986, y=0.979x+2.60) and (0.977, y=1.032x+0.158) respectively. In conclusion, the self-prepared reagents gave as satisfactory results for measurement of electrolytes as commercial reagents and can be reliably used for routine serum electrolytes measurement in a clinical chemistry laboratory.