Crystal structures are reported for three new sulfonyloxiranes 5, 6b and 7. Taken together with the structures previously reported for the two sulfonyloxiranes 1 and 2, these structures provide evidence of the existence of a generalised anomeric effect in 2-phenylsulfonyloxiranes, accounting for the substantial bond asymmetry in the oxirane ring, and thus for the reactivity of these oxiranes towards nucleophiles.