Abstract The one pot, three-components condensation of aromatic aldehydes, hydrazine and sulfur in ethanol under microwave irradiation provided symmetrically 3, 5-disubstituted 1, 3, 4-thiadiazoles in high yields and good purity. This reaction must be conducted under pressure of hydrogen sulfide produced in-situ. The structure of the compounds was confirmed by 1 H, 13 C NMR, MS and elemental analysis.