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Cardiac deformation may be measured by following radiopaque markers in 3-D with two X-ray cameras simultaneously. The 3-D positions of the markers can be reconstructed when (1) the camera geometry, and (2) the stereo correspondence are known. When observing large numbers (10-100) of identically shaped markers in an uncalibrated X-ray stereo camera set-up, both (1) and (2) are unknown. In the present study we developed a method to estimate (1) and (2) simultaneously from the sets of marker tracks obtained in the two views. In a computer simulation of 48 markers attached to a moving heart, 30% of the tracks were considered as missing, so only 24 stereo track pairs remained. On the average the method identified 23 pairs, 0.5% of which were false. Accurate estimates were obtained for the angles defining the camera geometry (RMS error 0.02/spl deg/ to 1/spl deg/).