Functional images of regional distribution of rapid filling (RF) rates have been developed and applied at rest and on exercise for regional analysis of 301 coronary artery territories (103 compromised by coronary narrowings, 198 normal). The observed time-interval of RF averaged 209 ms at rest (range 200 to 280) and 172 ms on exercise (range 125 to 200 ms). Normal RF is directed to the apex, and it is deviated from territories with reduced compliance to normal territories. Sensitivity in detection and localization of territories compromised by coronary narrowings exceeds 90% at rest for the anterior and infero-posterior wall and is higher than that obtained from systolic functional images. Specificity amounts also to over 90% and is much higher than that observed with systolic functional images. During RF, moderate to severe loss in compliance results in initial regional paradoxical inward motion in 40 to 45% of anterior or postero-inferior segments eventually accompanied by significant inward displacement of blood. Thus, with functional imaging of regional RF rates one can establish dysfunction and functional significance of coronary narrowings.