A technique for calibrating an x‐ray streak camerainsituhas been developed. It has been applied to an x‐ray streak camera installed on a collapsing gas shellZ‐pinch. The calibration was done by simultaneously measuring the emitted x‐rays using a pinhole camera, an InP:Fe photoconductive detector, and the streak camera. The spatial dimension of the streak image was calibrated by integrating the film density over time and fitting the resulting data to the corresponding information taken from an x‐ray pinhole image. The temporal calibration was obtained by similarly fitting the film density from the x‐ray streak image as a function of time integrated over the appropriate part of the spatial dimension with the signal from an InP:Fe photoconductive detector. By using this technique we have found a spatial magnification of the streak camera system consistent with the results derived from the geometrical optics to within 10%. A temporal dispersion of 2.5±0.5 ns/mm was obtained, which is in agreement with the nominal speed of 2.5 ns/mm. This technique also yielded an absolute intensity calibration of the streak camera.