Phosphite compounds represented by the formula
wherein R¹ stands for a tertiary hydrocarbyl group, R² stands for an alkyl group, an aralkyl group which may be substituted, an aryl group or a cycloalkyl group and n stands for 0, 1 or 2.
Such compounds possess stabilizing action against organic materials, particularly antioxidant action, and are useful as antioxidants for preventing deterioration by oxidation of organic materials.