The light chain of human low molecular mass kininogen consists of 38 amino acid residues. The half-cystine residue which forms the disulfide bridge to the heavy chain is located in the position 18. Alignment of the low molecular mass kininogen light chain with corresponding sections of other kininogens revealed that the N-terminal part of it is species specific and the C-terminal part is function specific. Furthermore, some internal homologies between various sections of the total molecule were found. A statistically significant sequence homology between the low molecular mass kininogen light chain and the C-terminal part of the ribonucleases was observed.