Vialykh, E. A., Ilarionov, S. A., Abdelrahman, H. M. and Vialykh, I. A. 2014. Changes in amino acids content of humic acids sequentially extracted from peat and sod-Podzolic soil. Can. J. Soil Sci. 94: 575-583. Amino acids (AA) and peptides are thought to be part of humic acids (HA), but debate whether they are an integral part of the HA is still going. Humic acids sequentially extracted from peat and sod-podzolic soil were analyzed for their AA content, elemental composition and by Fourier transform infrared spectroscopy. Extracted HA were hydrolyzed in 6 M HCl for 16 h for AA release, which was detected by a capillary electrophoresis system. Alanine, arginine, sum of aspartic acid and asparagine, sum of cysteic acid and cysteine, sum of glutamic acid and glutamine, glycine, histidine, leucine and isoleucine, lysine, methionine, phenylalanine, proline, serine, threonine, tyrosine, valine were identified. The total content of hydrolyzable AA in sod-Podzol HA increased by 6.2-8.2% with increasing the extraction cycles while an inverse tendency was observed for AA released from peat HA. Moreover, individual AA expressed as percentages of total AA were constant values with coefficients of variation lower than 20% for the studied HA.