The discovery of an ideal technique for sterilising contaminated respirators and other anesthesia equipment remains a major problems, The antimicrobial activities of a recently discovered disinfectant alktaline-glutaraldehyde(Cidex), studied in vitro against various species of bacteria and fungi. The antimicrobial activity tests were performed according to the modified Kolmer method. The testing organisms were cultured in broth media at 37 ℃ and 25 ℃ for 18 hours to 14 days, and the disinfectant was diluted with sterile distilled;water to 0.4% and 2.0%. One milliliter of cultured broth was transferred into disinfectant-containing media and after 1, 2, 5, 10, 20, 30 and 60 minutes, one loopful of the mateials was removed from the media and inoculated into the broth media. All of the subcultures were incubated at 37 ℃ for 24 hours and fungal subcultures were incubated at 25 ℃ for 14 days. Results were obtained as follows: 1) Most of the bacteria were completely growth-inhibited by treatment with 0.4% active alkaline-glutaraldehyde solution for 2 minutes except a few strains such as St. aureus, B. subtilis and M. tuberculosis, which required from 16 to 20 min. 2) Mycobacterium tuberculosis was relatively resistant but it could be growth-inhibited by treatment with 2.0% solution for 2 minutes. 3) Growth inhibiting of fungi could be obtained by treatment with 2.0% solution for 5 to 10 minutes.