PURPOSE: To provide a multifilament yarn having high hydrolysis resistance and aminolysis resistance as well as superior fiber characteristics and mechanical characteristics.

CONSTITUTION: The multifilament yarn having high hydrolysis resistance and aminolysis resistance and comprising polyester based on poly(1,4- cyclohexanedimethylene terephthalate) is characterized by that at least 85 mole % of the diol-derived groups of the polyester are 1,4-cyclohexanedimethylene groups and that a tenacity of ≤40 cN/tex and a post hydrolysis or aminolysis treatment strength are at least 85% of the original strength. The production process thereof is also provided.