We present in vitro and in vivo results for validation of a new localized noninvasive ultrasonic measurement of both tissue absorption and perfusion. The method employs sub-second low-intensity focused ultrasonic beams for generating brief temperature rise on the order of 1° C. The RF data from an imaging transducer is processed to produce noninvasive temperature estimate in the localized heated volume using speckle tracking or frequency-domain algorithms previously published  . Absorption can be obtained from the initial heating rate while perfusion can be estimated from the initial decay. Due to the small size of the heated spot, the noninvasive temperature estimation can produce results that are virtually free of thermal lensing effects. Furthermore, since the measurements are based on heating and decay rates, only the parameters of the transient bioheat equation (density and heat capacity) are needed for the estimate. Both ex-vivo and in vivo results have shown two-fold to three-fold increase in tissue absorption. For the ex vivo results, the change in absorption was estimated using direct fine wire thermocouple measurements at the treatment site in addition to the noninvasive temperature estimation. The decay rate of the in vivo estimated temperature was observed to increase by two-fold indicating increased perfusion in the tumor surrounding the small lesion. While the opposite effect can be expected in volumetric lesion formation, this is very likely in this single-shot lesion formation experiment. In any event, the in vivo results show very clearly the feasibility of estimating perfusion based on decay rate.