A technique for determining the instantaneous heat release from a localized region of a flame and correlating it with the fluctuating pressure is described. The technique is based on ultraviolet at 307 nm by the chemiluminescence of the OH* radical, which is closely associated with the combustion reactions in gaseous hydrocarbon flames. A novel feature of the approach is the use of the rms fluctuations in signal rather than the mean level as the indicator of mean turbulent heat release. Two lines-of-sight intersecting in the flame at right angles are used to determine the radial distribution of emission from the product of the signals. It is shown that this is a measure of the emission within an integral length scale of the point of intersection, provided only that the collection widths are smaller than this scale. Results of applying this novel technique to a premixed swirling flame under conditions of low acoustic self-excitation are presented. These results are compared with those obtained by deconvoluting the line-of-sight signals from a traverse across the flame radius, and good correspondence is obtained. However, when there is significant acoustic excitation, the integral scale of the flame fluctuations is the entire flame diameter and so the product must be restricted to frequencies other than those which are acoustically excited, if the background heat release distribution is to be obtained. The radial distribution of the acoustically coupled component of heat release can then only be determined from the deconvolution of the line-of-sight signals.