AbstractA study of the α‐cleavage processes of aliphatic amines (using RLCH2N(R)CH2Rs and RLCH(NR)RsRL represents the larger Rs the smaller alkyl group throughout this paper and both, unless indicated to the contrary, have similar degrees of lsubstitution on the α‐carbon atom. as typical substrates) at several ionizing voltages indicates that the loss ratio of large and small alkyl radicals, [M RL]/[M Rs], decreases with ionizing voltage. This ratio, greater than 1·0 at 70 eV, may become less than unity at low voltage (15 eV, 10 eV) in some cases. Comparison of similarly structured compounds with nitrogen or oxygen as the heteroatom suggests that the effects of ionizing voltage are lessened when the fragment is of greater stability (e.g. amine vs. ether or imine vs. ketone). The effects of lowering the ionizing voltage became much less pronounced as the alkyl groups become larger or similar in size.