An image based method for transient surface normal heat flux calculation from thermographic data is suggested. It is based on an analytical solution of the three-dimensional linear heat conduction equation. The method yields correct results for the surface normal heat flux even in regions with strong lateral gradients by taking into account the transient surface temperature of an area surrounding each evaluation point within the thermographic image. The solution for the heat flux can be stabilized with respect to measurement errors by an iterative regularization method. The validation of the method in synthetic test cases indicates its good accuracy over a broad range of Fourier numbers. (c) 2006 Elsevier Ltd. All rights reserved.