Abstract The electron distribution for Cl,O bonds in a wide range of molecules is analyzed using Bader’s atoms in molecules theory (QTAIM) and measures of bond order. It is shown that the electron density and energy density at the bond critical point correlate very well with bond length, but the Laplacian shows no simple relationship; charge transfer is shown to be responsible for the anomalous behavior. Measures of bond order show a more complex behavior, but a combination of bond order and polarity correlates well with bond length and electron density. The analysis provides several lines of evidence for multiple bonding in the uni-coordinate Cl,O bonds of the molecules. A comparison of a sub-set of results for DFT and CCSD(T) wavefunctions shows their similar behavior.