The surface tension of binary mixtures near critical endpoints is discussed with detailed focus on the composition dependence. The similarity with the corresponding composition dependence of the vapor pressure is explored. The differences between mixtures in which the more volatile component is of lower surface tension, i.e. is less tense-known as usual mixtures-and those in which the more volatile component is more tense-known as unusual mixtures-are analyzed. As a basis of discussion, a limited review of the related literature is presented along with some fresh results for two usual mixtures (octamethylcyclotetrasiloxane + perfluoropentane and heptane + perfluorohexane) and two unusual mixtures (pentane + perfluoroheptane and 2-methylpentane + perfluorotributylamine). These mixtures display a variety of horizontal inflections characteristic of the behavior of the noncritical interface near a critical endpoint. The form of the horizontal inflection is uniformly related to the sign of the difference between the surface tensions of the pure components, i.e. with the overall negative slope towards the less tense component. A number of the mixtures also exhibit aneotropy or surface azeotropy. All these results are shown to be well described by the Surface Regular Solution theory.