Surface tensions of pure organic compounds and their dilute aqueous solutions (molar fraction typically x(2) < 0.015) at 298.15 K have been measured. The Szyszkowski equation has been used for correlation of the experimental surface tension data, and the ability of the equation to describe the concentration dependence of surface tension has been tested. When accurate values of surface tension were known, the Szyszkowski equation has been found to not be suitable for correlation, especially in the case when values of the first derivative, obtained from the parameters of a correlation equation, have been wanted. Therefore values of limiting slopes of surface pressure concentration dependence have been evaluated by a linear regression of the most dilute results (typically x(2) < 0.001).