The curing behavior and properties of bismaleimide (BMI), bisoxazoline (1,3-PBO), and oleic acid ternary copolymers are investigated. It is found that the cure temperature of BMI/1,3-PBO or BMI/1,3-PBO/oleic acid could be lowered, compared with that of BMI. The reason lies in the copolymerization reaction between BMI, 1,3-PBO, and oleic acid. SEM results confirm that 1,3-PBO and oleic acid could toughen BMI system because of the formation of ester-amide bonds and the long fat chain of oleic acid. The cured resins from BMI/1,3-PBO or BMI/1,3-PBO/oleic acid have superior heat resistance and water resistance, (C) 2008 Wiley Periodicals, Inc.