In the title compound, C6H4N4S3, the 1,3,4-thiadiazole ring is essentially planar, with an r.m.s. deviation of 0.001 angstrom. The two N-C-S-C torsion angles in the molecule are -23.41 (15) and 0.62 (14)degrees. One acetonitrile group is above the plane of the 1,3,4-thiadiazole ring and the other is below it, indicating syn and anti orientations. In the crystal, C-H center dot center dot center dot N hydrogen bonds link the molecules into ribbons along .