AbstractSemiempirical molecular orbital calculations by theMNDOmethod are reported for sulfur rings and chains S3through S8, for the corresponding dications, S 22+through S 82+, and for S 4+. TheMNDOmethod seems quite successful in predicting the geometries of neutral catenated sulfur molecules, even the unusual bond‐length alternation and extent of coplanarity incyclo‐S7. In contrast to hydrocarbon rings, for which its prediction of strain is erratic,MNDOis consistent in its calculated strain energies in small cyclosulfur rings; unfortunately all the strain energies are overestimated by 70%. As a consequence of this error, the method must be considered unreliable in its predictions of structures for the dications S n2+, since many of these ions could potentially exist as strained bicyclic systems. In addition,MNDOappears to have difficulty handling long, partial SS σ bonds, as are found to occur in S 82+. It may be for this reason thatMNDOpredicts, apparently incorrectly, that the open‐chain isomers of S n2+are more stable than are any of the cyclic forms, at least for S 52+to S 82+. With respect to neutral Snmolecules, however, theMNDOpredictions appear more reliable thanab initiomolecular orbital (MO) calculations using small basis sets without polarization functions and without configuration interaction (CI). However,MNDOapparently underestimates by about a factor of two the strength of the three‐electron π bonds present in the terminal links o