A simple, rapid and sensitive luminescence spectrometry is described for the determination of some β- lactamic antibiotics in pure form and in pharmaceutical formulations. The proposed method is based on the fact that the redox reaction between cerium(IV) and β-lactamic antibiotics in an acidic medium to form Ce(III), which can luminesce, and sodium has great enhancement for the luminescence intensity of Ce(III). The method permits the determination of 8.0x10−6−2.0x10−3mg/ml, 1.0x10−5−2.0x10−3mg/ml, 2.0x10−5−2.5x10−3mg/ml, and 2.0x10−5−3.0x10−3mg/ml for cepharadine, cefalexin, 6-aminopenicillanic acid (6-APA) and cefazolin respectively. Their detection limits (S/N=3) were 2.0x10−6mg/ml, 7.0x10−6mg/ml, 6.0x10−6mg/ml, and 8.0x10−6mg/ml, respectively.