In order to examine antibiotic activities of cefteram (CFTM), its minimum inhibitory concentrations (MIC's) and those of other cephem drugs were determined against clinically isolated strains received from July 1990 to June 1991 and from July 1992 to February 1993 from medical facilities throughout the country and against clinically isolated strains detected in our laboratory in samples from patients with various infectious diseases. The obtained results are summarized below. 1. No CFTM-resistant strains were found among beta-streptococci, Klebsiella spp., Proteus mirabilis, Haemophilus influenzae, and Neisseria gonorrhoeae or even when found, they were present in extremely low proportions. 2. It appeared that Streptococcus pneumoniae insensitive or resistant to beta-lactams, as well as cephems-resistant strains of Escherichia coli were increasing. The former included benzylpenicillin (PCG)-insensitive S. pneumoniae (PISP) of PCG-resistant S. pneumoniae (PRSP), and the presence of the latter suggests the possibility of the existence of "Extended broad-spectrum beta-lactamase" producing strains. The MIC's of beta-lactams against the above PISP or PRSP, and against cephems-resistant E. coli tended to be high, but those of CFTM were relatively low (in most cases). 3. Proportions of strains resistant to cephems, including CFTM among Citrobacter spp., Enterobacter spp., Serratia marcescens, Proteus vulgaris, Morganella morganii, and Providencia rettgeri were high, and in addition, the existence of these cephem resistant species suggests an increase in multiple drug resistant strains that show resistance to new quinolone drugs. 4. As mentioned above, CFTM is by no means a perfect drug or utility drug and its antimicrobial activities do not cover some recent isolates with multiple drug resistance. Except problems encountered with so-called "attenuated" strains of bacteria, increases in resistance can only be observed at a level of MIC90's, and as far as MIC80's are concerned, CFTM still is as active as before and may be used in the treatment of most infections we encounter in normal medical practices.