I read the paper "Effect of concentration of dispersed organic matter on optical maturity parameters. Inter laboratory results of the organic matter concentration working group of the ICCP" by Mendonca Filho et al. (2010). Although the subject of the paper is significant, I disagree with the methodology of the project, its results have some inherent limitations and need further evaluation for reliability in deciphering the effect of concentration of dispersed organic matter on optical maturity parameters. (C) 2010 Elsevier B.V. All rights reserved.