Red-Yellow and related soils in the Philippines consisted of Red soils, Yellow soils, Dark Brown soils, Terra Rossa-like soils, Terra Fusca-like soils, Rendzina-like soils, Brown Upland soils, Pseudogley-like soils, Andosols, Vertisols, Brown Lowland soils, and Gray Lowland soils. The acidity tended to decrease in the order: Red soils > Yellow soils > Dark Brown soils > Terra Rossa-like soils > Terra Fusca-like soils > Rendzina-like soils. The acidity of other soil groups showed a wide range depending on the lime contents of parent materials and the duration of the dry period in the area. The factors that control the properties and the distribution patters of Red-Yellow and related soils in the Philippines were found to be: parent materials, land form, and types of climate based on the duration of the dry period.