To study the stability of 17β-lactams to 16 standard β-lactamases. Methods Spectrophotometrical technology was used. Results The third generation cephalosporins and aztreonam were stable to β-lactamases except cefoperazone

which had poor stability.Ceftriaxone was the most resistant agent in the eight tested third generation cephalosporins

the relative hydrolysis rates (RHRS) of the former was less than 30%. Conclusion RHRS of cefuroxime the second generation cephalosporin

were 6%-65%. The stability of the first generation cephalosporins to β-lactamases was poorer than those of the second generation cephalasporins. Among the first generation cephalosporins

cefathiamidine was the most susceptible to β-lactamases

and the RHRS by OXA-2

SHV-4

and D31 were 523%

912% and 359% respectively. The penicillins were susceptible to β-lactamases and RHRS were more than 100%.