Cyclo(L-Trp-L-Trp) is an antibiotic, and shows antimicrobial activity. Cyclo(L-Trp-L-Trp) can inhibit A. baumannii, as well as Candida albicans, Bacillus subtilis, Micrococcus luteus, Saccharomyces cerevisiae, Aspergillus niger, Staphylococcus aureus. Cyclo(L-Trp-L-Trp) can be used in microbial infection research.