Changes in systolic (SP), diastolic (DP), and pulse pressures (PP) caused by various stress-induced changes (hypoxia, anemia, hypercarbia, halothane, cyclopropane) in heart rate (HR), stroke volume (SV), and total peripheral resistance (TPR) were studied in dogs and man. Pooled data from 13 separate studies (n = 85) revealed highly significant correlations of ΔSP with ΔDP (r = 0.88), and ΔSP with ΔSV (r = 0.82) only. There was no correlation of ΔSP or ΔDP with either ΔTPR or ΔHR. ΔDP correlated poorly with ΔSV, and ΔPP correlated poorly with all variables. Changes in TPR and SV could not be inferred from ΔDP or ΔPP, respectively. Within each individual group, few correlations were found except for ΔSP with ΔDP. Inferences made from diastolic or pulse-pressure measurements on the state of the circulation, particularly TPR and SV, are misleading and do not add to knowledge obtained from measurement of systolic pressure alone.