Past research has associated ABO blood type and mental stress with cardiovascular risk. We studied the effects of blood type (A vs. O) coupled with a mirror drawing stressor on very low density lipoprotein toxicity-preventing activity (TxPA) and plasma cortisol levels. Exposure to the stressor significantly decreased TxPA and increased cortisol for the total group of 25 older adult males. However, the stress response patterns of the 15 blood type A males were different from those of the 10 type O subjects. The blood type A group had higher initial levels of TxPA and cortisol as well as quicker stress recovery rates than the type O group. ABO blood type may be an important behavioral hematologic variable to assess in studies concerning biochemical stress response or cardiovascular risk.