The intramolecular nonbonded 1, 5-type S⊙⊙⊙ O interactions are recognized in the crystalline structures of the (acylimino) thiadiazoline derivatives (1-3) as angiotensin II receptor antagonists. The relative stability of the nonbonded 1, 5-type S⊙⊙⊙ O interaction was investigated using the X-ray crystallographic analyses and the ab initio MO calculations (HF/3-21G*, 6-31G*, and 6-311+ G**) of the simplified model compounds (6, 7, and 9). ...