First synthesis of N- and S-alpha-l-arabinopyranosyl[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles is described. Antimicrobial screening of two selected regioisomeric compounds against Aspergillus fumigatus, Penicillium italicum, Syncephalastrum racemosum, Candida albicans, Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus subtilis and Escherichia coli are compared.