The aim of this paper is to investigate the bonding in simple ylides in a physically meaningful fashion. Simple ylides have unique electronic structures because the behavior of electrons in the compounds does not conform to that expected solely on the basis of carbon-carbon and carbon-hydrogen bonds. The C S bonds in the molecules SH 2 CH 2 and (CH 3 ) 2 SCH 2 are investigated by using the sharing amplitudes and the sharing indices [R.L. Fulton, J. Chem. Phys. 97 (1993) 7516]. The sharing indices between the carbon and the sulfur indicate an intermediate single-double bond character in the ylides. On the basis of the group basin charges and the inter-group sharing indices between the CH 2 groups and the SH 2 or S(CH 3 ) 2 groups, the bonds are ionic with full double bond characters. Detailed comparisons of the results for the ylides PHCH 2 , PH 3 CH 2 , SH 2 CH 2 and NH 3 CH 2 are presented.