We examined the ability of baseline measures of receptors (lymphocyte beta-adrenergic) and nonreceptors (plasma catecholamines, heart rate, and blood pressure) to predict cardiovascular responses to a mental arithmetic task. Twenty-five male volunteers served as subjects. Nonreceptor measures predicted the heart rate response to stress poorly (p = 0.67). However, beta receptor density and sensitivity explained 48.4% of the variance in heart rate response (p = 0.007). When both receptor and nonreceptor measures were used together, they predicted 76.6% of the variance (p = 0.005), which was more than was explained by either receptor or nonreceptor baseline measurements alone (p = 0.001). Receptor measures may thus greatly improve the prediction of reactivity.