It is extremely important to prevent opportunistic and hospital infection. Therefore, bacterial contamination of instruments, equipment and floors is frequently checked. MacConkey agar(Mac agar)is routinely to dtect Gram negatiue rods(GNR), caustive organisms of opportvnistic or hospital infection.However,only a few colonies of GNR were detected from hospital floors on Mac agar, while many colonies of GMR were detected on brain heart infusion agar (BHIA). It is thought that the 0.1% of bile salts in Mac agar is too inhibitory for the growth of GNR existing on floors. Therefore a new medium for the detection of GNR form floors was developed.Firitly. bacteria obtained by swabbing a floor were inocunlted on Drigalski agar containing desoxycolate(DOC) at various concetrations.Drigalski agar containing 0.03% DOC(D-D agar) was found to be suitable for the growth of GNR, while at the same time suppressing the growth of GPC. Secondly, D-D agar,Mac agar and BHIA were used to detect GNR adhering on gless plates. 50-80% CFU of the total GNR grown on BHIA were detected on D-D agar, but only 10-20% CFU were detected on Mac agar. Thirdly, these agars were uned to detect GNR on floors and the hands of nurses. D-D agar was apparently better than Mac agar. Consequently, D-D agar is very ureful for the selective detection of GNR on floors and hands.