The electron distribution for S,O bonds in a wide range of molecules is analyzed using Bader's atoms in molecules theory (AIM) and measures of bond order. It is shown that the electron density and other derived parameters at the bond critical point correlate very well with bond length. Measures of bond order show a more complex behavior, but a combination of bond order and polarity correlates well with bond length. The trends shown in the properties of derived parameters demonstrate clear characteristics for polar covalent bonds and for recognition of multiple bonding in many of the molecules.