In cryo-electron microscopy of vitreously frozen biological specimens, phase-plate imaging can greatly increase the signal-to-noise ratio of the micrographs. When routinely used, this imaging technique may be the method of choice for cryo-electron tomography, in which each image in the tilt-series data set suffers from a high noise background due to the low-electron-dose exposure. Utilizing the Zernike phase-contrast imaging technique, we have carried out an electron tomographic study of the axonemal microtubule doublets and their associated radial spokes. The reconstructed tomogram displays a strong contrast. The quality of the resultant density maps, obtained by sub-volume averaging of a single tomogram in this study, is comparable with that from the averaging of many cryo-tomograms without using the phase-plate.